feat: add Printify webhook endpoint for real-time product updates

- Add /webhooks/printify endpoint with HMAC-SHA256 signature verification
- Add Webhooks context to handle product:updated, product:deleted events
- Add ProductDeleteWorker for async product deletion
- Add webhook API methods to Printify client (create, list, delete)
- Add register_webhooks/2 to Printify provider
- Add mix register_webhooks task for one-time webhook registration
- Cache raw request body in endpoint for signature verification

Usage:
1. Generate webhook secret: openssl rand -hex 20
2. Add to provider connection config as "webhook_secret"
3. Register with Printify: mix register_webhooks https://yourshop.com/webhooks/printify

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

test/simpleshop_theme/webhooks/product_delete_worker_test.exs

@@ -0,0 +1,48 @@
+defmodule SimpleshopTheme.Webhooks.ProductDeleteWorkerTest do
+  use SimpleshopTheme.DataCase
+  use Oban.Testing, repo: SimpleshopTheme.Repo
+
+  alias SimpleshopTheme.Webhooks.ProductDeleteWorker
+  alias SimpleshopTheme.Products
+
+  import SimpleshopTheme.ProductsFixtures
+
+  describe "perform/1" do
+    test "deletes product when found" do
+      conn = provider_connection_fixture(%{provider_type: "printify"})
+
+      {:ok, product, :created} =
+        Products.upsert_product(conn, %{
+          provider_product_id: "test-product-123",
+          title: "Test Product",
+          provider_data: %{}
+        })
+
+      assert Products.get_product(product.id) != nil
+
+      assert :ok =
+               perform_job(ProductDeleteWorker, %{
+                 provider_product_id: "test-product-123"
+               })
+
+      assert Products.get_product(product.id) == nil
+    end
+
+    test "returns ok when product not found" do
+      _conn = provider_connection_fixture(%{provider_type: "printify"})
+
+      assert :ok =
+               perform_job(ProductDeleteWorker, %{
+                 provider_product_id: "nonexistent-product"
+               })
+    end
+
+    test "cancels when no provider connection" do
+      # No connection created
+      assert {:cancel, :no_connection} =
+               perform_job(ProductDeleteWorker, %{
+                 provider_product_id: "test-product-123"
+               })
+    end
+  end
+end

test/simpleshop_theme/webhooks_test.exs

@@ -0,0 +1,65 @@
+defmodule SimpleshopTheme.WebhooksTest do
+  use SimpleshopTheme.DataCase
+
+  alias SimpleshopTheme.Webhooks
+
+  import SimpleshopTheme.ProductsFixtures
+
+  setup do
+    conn = provider_connection_fixture(%{provider_type: "printify"})
+    {:ok, provider_connection: conn}
+  end
+
+  describe "handle_printify_event/2" do
+    test "product:updated triggers sync", %{provider_connection: _conn} do
+      # With inline Oban, the job executes immediately (and fails due to no real API key)
+      # But the handler should still return {:ok, _} after inserting the job
+      result =
+        Webhooks.handle_printify_event(
+          "product:updated",
+          %{"id" => "123", "shop_id" => "456"}
+        )
+
+      assert {:ok, %Oban.Job{}} = result
+    end
+
+    test "product:publish:started triggers sync", %{provider_connection: _conn} do
+      result =
+        Webhooks.handle_printify_event(
+          "product:publish:started",
+          %{"id" => "123"}
+        )
+
+      assert {:ok, %Oban.Job{}} = result
+    end
+
+    test "product:deleted triggers delete", %{provider_connection: _conn} do
+      result =
+        Webhooks.handle_printify_event(
+          "product:deleted",
+          %{"id" => "123"}
+        )
+
+      assert {:ok, %Oban.Job{}} = result
+    end
+
+    test "shop:disconnected returns ok" do
+      assert :ok = Webhooks.handle_printify_event("shop:disconnected", %{})
+    end
+
+    test "unknown event returns ok" do
+      assert :ok = Webhooks.handle_printify_event("unknown:event", %{})
+    end
+
+    test "returns error when no provider connection" do
+      # Delete all connections first
+      SimpleshopTheme.Repo.delete_all(SimpleshopTheme.Products.ProviderConnection)
+
+      assert {:error, :no_connection} =
+               Webhooks.handle_printify_event(
+                 "product:updated",
+                 %{"id" => "123"}
+               )
+    end
+  end
+end