add admin email settings page with provider selection

Card radio component for picking email providers (SMTP, SendGrid, Mailjet, etc.)
with instant client-side switching via JS hook. Adapter configs are pre-rendered
and toggled without a server round-trip. Secrets are preserved when re-saving
with blank password fields. Includes from address field, test email sending,
and disconnect flow.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

lib/berrypod/application.ex

@@ -16,6 +16,8 @@ defmodule Berrypod.Application do
       Supervisor.child_spec({Task, &Berrypod.Release.seed_defaults/0}, id: :seed_defaults),
       # Load encrypted secrets from DB into Application env
       {Task, &Berrypod.Secrets.load_all/0},
+      # Load email adapter config from DB (after secrets are available)
+      Supervisor.child_spec({Task, &Berrypod.Mailer.load_config/0}, id: :load_email_config),
       {DNSCluster, query: Application.get_env(:berrypod, :dns_cluster_query) || :ignore},
       {Phoenix.PubSub, name: Berrypod.PubSub},
       # Background job processing

lib/berrypod/mailer.ex

@@ -1,6 +1,9 @@
 defmodule Berrypod.Mailer do
   use Swoosh.Mailer, otp_app: :berrypod
 
+  alias Berrypod.Mailer.Adapters
+  alias Berrypod.Settings
+
   @doc """
   Returns whether a real email adapter is configured.
 
@@ -11,4 +14,137 @@ defmodule Berrypod.Mailer do
     adapter = Application.get_env(:berrypod, __MODULE__)[:adapter]
     adapter != nil and adapter != Swoosh.Adapters.Local
   end
+
+  @doc """
+  Returns true if email is configured via environment variables (SMTP_HOST).
+
+  When env vars are active, the admin UI shows the config as read-only.
+  """
+  def env_var_configured? do
+    System.get_env("SMTP_HOST") != nil
+  end
+
+  @doc """
+  Returns the current adapter key and config for display in the admin UI.
+
+  Returns `{adapter_key, config_map}` or `{nil, %{}}` if using the default.
+  """
+  def current_config do
+    mailer_config = Application.get_env(:berrypod, __MODULE__, [])
+    adapter = mailer_config[:adapter]
+
+    case Enum.find(Adapters.all(), &(&1.module == adapter)) do
+      nil ->
+        {nil, %{}}
+
+      adapter_info ->
+        config =
+          for field <- adapter_info.fields, into: %{} do
+            value =
+              case field.type do
+                :secret -> Settings.secret_hint("email_#{field.key}")
+                _ -> Settings.get_setting("email_#{field.key}")
+              end
+
+            {field.key, value}
+          end
+
+        {adapter_info.key, config}
+    end
+  end
+
+  @doc """
+  Loads email config from the Settings table and applies it to Application env.
+
+  Env vars take precedence — if SMTP_HOST is set, this is a no-op since
+  runtime.exs already configured the adapter.
+
+  Called on boot (from Application.start) and after admin saves email settings.
+  """
+  def load_config do
+    if env_var_configured?() do
+      :ok
+    else
+      case Settings.get_setting("email_adapter") do
+        nil ->
+          :ok
+
+        adapter_key ->
+          case Adapters.get(adapter_key) do
+            nil ->
+              :ok
+
+            adapter_info ->
+              config = build_config(adapter_info)
+              Application.put_env(:berrypod, __MODULE__, config)
+              # API-based adapters need a real HTTP client (dev defaults to false)
+              if adapter_info.module != Swoosh.Adapters.SMTP do
+                Application.put_env(:swoosh, :api_client, Swoosh.ApiClient.Req)
+              end
+
+              :ok
+          end
+      end
+    end
+  end
+
+  @doc """
+  Sends a test email to the given address using the current config.
+  """
+  def send_test_email(to_address, from \\ nil) do
+    import Swoosh.Email
+
+    email =
+      new()
+      |> to(to_address)
+      |> from({"Berrypod", from || from_address()})
+      |> subject("Berrypod test email")
+      |> text_body("This is a test email from your Berrypod shop. Email delivery is working.")
+
+    deliver(email)
+  end
+
+  @doc "Returns the configured from address for outbound email."
+  def from_address do
+    Settings.get_setting("email_from_address") || "noreply@#{default_from_domain()}"
+  end
+
+  # Build Swoosh config keyword list from Settings for a given adapter
+  defp build_config(adapter_info) do
+    opts =
+      for field <- adapter_info.fields, reduce: [] do
+        acc ->
+          settings_key = "email_#{field.key}"
+
+          value =
+            case field.type do
+              :secret -> Settings.get_secret(settings_key)
+              _ -> Settings.get_setting(settings_key)
+            end
+
+          case {value, field} do
+            {nil, _} ->
+              acc
+
+            {val, %{type: :integer}} ->
+              [{String.to_atom(field.key), to_integer(val)} | acc]
+
+            {val, _} ->
+              [{String.to_atom(field.key), val} | acc]
+          end
+      end
+
+    # SMTP uses :relay, others use the native Swoosh key names
+    [{:adapter, adapter_info.module} | opts]
+  end
+
+  defp to_integer(val) when is_integer(val), do: val
+  defp to_integer(val) when is_binary(val), do: String.to_integer(val)
+
+  defp default_from_domain do
+    case Application.get_env(:berrypod, BerrypodWeb.Endpoint)[:url][:host] do
+      nil -> "example.com"
+      host -> host
+    end
+  end
 end

lib/berrypod/mailer/adapter.ex

@@ -0,0 +1,5 @@
+defmodule Berrypod.Mailer.Adapter do
+  @moduledoc false
+  @enforce_keys [:key, :name, :module, :description, :tags, :fields]
+  defstruct [:key, :name, :module, :description, :tags, :fields, url: nil]
+end

lib/berrypod/mailer/adapters.ex

@@ -0,0 +1,140 @@
+defmodule Berrypod.Mailer.Adapters do
+  @moduledoc """
+  Registry of supported email adapters and their config shapes.
+
+  Each adapter entry defines the fields needed for configuration.
+  The UI renders dynamically from this registry. Adding a new adapter
+  is just adding an entry here — no other code changes needed.
+  """
+
+  alias Berrypod.Mailer.{Adapter, Field}
+
+  # Ordered by capability: transactional + marketing first,
+  # then transactional only, then self-hosted.
+  @adapters [
+    %Adapter{
+      key: "smtp",
+      name: "SMTP",
+      module: Swoosh.Adapters.SMTP,
+      description: "Connect to any email server via SMTP. Works with most providers and hosts.",
+      tags: ["All email", "Any provider"],
+      fields: [
+        %Field{key: "relay", label: "Server host", type: :string, required: true},
+        %Field{key: "port", label: "Port", type: :integer, default: 587},
+        %Field{key: "username", label: "Username", type: :string},
+        %Field{key: "password", label: "Password", type: :secret}
+      ]
+    },
+    %Adapter{
+      key: "sendgrid",
+      name: "SendGrid",
+      module: Swoosh.Adapters.Sendgrid,
+      description: "Generous free tier, widely used.",
+      tags: ["All email", "US"],
+      url: "https://sendgrid.com",
+      fields: [
+        %Field{key: "api_key", label: "API key", type: :secret, required: true}
+      ]
+    },
+    %Adapter{
+      key: "brevo",
+      name: "Brevo",
+      module: Swoosh.Adapters.Brevo,
+      description: "All-in-one platform, GDPR-friendly.",
+      tags: ["All email", "France", "GDPR"],
+      url: "https://www.brevo.com",
+      fields: [
+        %Field{key: "api_key", label: "API key", type: :secret, required: true}
+      ]
+    },
+    %Adapter{
+      key: "mailjet",
+      name: "Mailjet",
+      module: Swoosh.Adapters.Mailjet,
+      description: "EU data processing, good free tier.",
+      tags: ["All email", "France", "GDPR"],
+      url: "https://www.mailjet.com",
+      fields: [
+        %Field{key: "api_key", label: "API key", type: :secret, required: true},
+        %Field{key: "secret", label: "Secret key", type: :secret, required: true}
+      ]
+    },
+    %Adapter{
+      key: "resend",
+      name: "Resend",
+      module: Swoosh.Adapters.Resend,
+      description: "Developer-friendly API, simple setup.",
+      tags: ["Transactional", "US"],
+      url: "https://resend.com",
+      fields: [
+        %Field{key: "api_key", label: "API key", type: :secret, required: true}
+      ]
+    },
+    %Adapter{
+      key: "mailgun",
+      name: "Mailgun",
+      module: Swoosh.Adapters.Mailgun,
+      description: "EU region option available.",
+      tags: ["Transactional", "EU option", "Sweden"],
+      url: "https://www.mailgun.com",
+      fields: [
+        %Field{key: "api_key", label: "API key", type: :secret, required: true},
+        %Field{key: "domain", label: "Domain", type: :string, required: true}
+      ]
+    },
+    %Adapter{
+      key: "postmark",
+      name: "Postmark",
+      module: Swoosh.Adapters.Postmark,
+      description: "Excellent deliverability tracking.",
+      tags: ["Transactional", "US"],
+      url: "https://postmarkapp.com",
+      fields: [
+        %Field{key: "api_key", label: "API key", type: :secret, required: true}
+      ]
+    },
+    %Adapter{
+      key: "mailpace",
+      name: "MailPace",
+      module: Swoosh.Adapters.MailPace,
+      description: "Privacy-focused, simple API.",
+      tags: ["Transactional", "UK"],
+      url: "https://mailpace.com",
+      fields: [
+        %Field{key: "api_key", label: "API key", type: :secret, required: true}
+      ]
+    },
+    %Adapter{
+      key: "postal",
+      name: "Postal",
+      module: Swoosh.Adapters.Postal,
+      description: "Full control over your email infrastructure.",
+      tags: ["All email", "Self-hosted", "Open source"],
+      url: "https://docs.postalserver.io",
+      fields: [
+        %Field{key: "api_key", label: "API key", type: :secret, required: true},
+        %Field{key: "base_url", label: "Server URL", type: :string, required: true}
+      ]
+    }
+  ]
+
+  @doc "Returns all supported adapters."
+  def all, do: @adapters
+
+  @doc "Returns an adapter by its string key, or nil."
+  def get(key) when is_binary(key) do
+    Enum.find(@adapters, &(&1.key == key))
+  end
+
+  @doc "Returns the settings keys for an adapter's fields (prefixed with `email_`)."
+  def field_keys(%{fields: fields}) do
+    Enum.map(fields, &"email_#{&1.key}")
+  end
+
+  @doc "Returns all possible settings keys across all adapters."
+  def all_field_keys do
+    @adapters
+    |> Enum.flat_map(&field_keys/1)
+    |> Enum.uniq()
+  end
+end

lib/berrypod/mailer/field.ex

@@ -0,0 +1,5 @@
+defmodule Berrypod.Mailer.Field do
+  @moduledoc false
+  @enforce_keys [:key, :label, :type]
+  defstruct [:key, :label, :type, :default, required: false]
+end