namespace email settings keys per adapter

Settings keys like api_key were shared across providers, so switching
from e.g. Postmark to SendGrid showed the old API key. Now each
adapter gets its own namespaced key (email_postmark_api_key, etc.)
so credentials persist independently and switching back pre-fills
previously saved values.

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

lib/berrypod_web/live/admin/email_settings.ex

@@ -30,6 +30,26 @@ defmodule BerrypodWeb.Admin.EmailSettings do
      |> assign(:form, to_form(%{}, as: :email))}
   end
 
+  defp load_adapter_values(adapter_key) do
+    case Adapters.get(adapter_key) do
+      nil ->
+        %{}
+
+      adapter_info ->
+        for field <- adapter_info.fields, into: %{} do
+          settings_key = Adapters.settings_key(adapter_key, field.key)
+
+          value =
+            case field.type do
+              :secret -> Settings.secret_hint(settings_key)
+              _ -> Settings.get_setting(settings_key)
+            end
+
+          {field.key, value}
+        end
+    end
+  end
+
   defp provider_options do
     Enum.map(Adapters.all(), fn adapter ->
       %{
@@ -44,7 +64,8 @@ defmodule BerrypodWeb.Admin.EmailSettings do
 
   @impl true
   def handle_event("change_adapter", %{"email" => %{"adapter" => key}}, socket) do
-    {:noreply, assign(socket, :adapter_key, key)}
+    values = load_adapter_values(key)
+    {:noreply, socket |> assign(:adapter_key, key) |> assign(:current_values, values)}
   end
 
   def handle_event("save", %{"email" => params}, socket) do
@@ -113,8 +134,9 @@ defmodule BerrypodWeb.Admin.EmailSettings do
       |> Enum.filter(fn field ->
         val = params[field.key]
         empty = is_nil(val) or val == ""
+        settings_key = Adapters.settings_key(adapter_info.key, field.key)
         # Secret fields can be left blank to keep existing value
-        empty and not (field.type == :secret and Settings.get_secret("email_#{field.key}") != nil)
+        empty and not (field.type == :secret and Settings.get_secret(settings_key) != nil)
       end)
 
     if missing != [] do
@@ -124,17 +146,10 @@ defmodule BerrypodWeb.Admin.EmailSettings do
       # Save adapter type
       Settings.put_setting("email_adapter", adapter_info.key)
 
-      # Clear fields from other adapters
-      current_keys = MapSet.new(Enum.map(adapter_info.fields, &"email_#{&1.key}"))
-
-      for key <- Adapters.all_field_keys(), key not in current_keys do
-        Settings.delete_setting(key)
-      end
-
       # Save current adapter fields (blank secrets keep existing value)
       for field <- adapter_info.fields do
         value = params[field.key]
-        settings_key = "email_#{field.key}"
+        settings_key = Adapters.settings_key(adapter_info.key, field.key)
 
         cond do
           value && value != "" ->