fix: purge the host site cache on Journal API post writes

Admin saves purged the site cache; the token API's create, update,
delete and featured-image writes did not, so API-published posts waited
for the site's cache TTL.

site_cache_admin_test.go

@@ -387,3 +387,36 @@ func TestCategoriesAdminFrameworkKeysWin(t *testing.T) {
 		t.Fatalf("the deprecated Journal target got %d requests: %+v", len(got), got)
 	}
 }
+
+// TestJournalAPIPurgesSiteCache proves the token API's post writes purge
+// the host site's cache like admin saves: create, update and delete each
+// send one purge with kind post and the post's slug.
+func TestJournalAPIPurgesSiteCache(t *testing.T) {
+	recv := newPurgeReceiver(t)
+	env := newPostsEnv(t, recv.env()...)
+	recv.drainFrom(t, env.app)
+	token := env.admin(t, controllers.PermissionAccessPosts)
+
+	rec := env.expect(t, http.StatusCreated, http.MethodPost, "/_journal/api/v1/posts", token, map[string]any{
+		"title":   "Api purge",
+		"content": "Before",
+	})
+	var created struct {
+		Data struct {
+			ID   uint   `json:"id"`
+			Slug string `json:"slug"`
+		} `json:"data"`
+	}
+	if err := json.Unmarshal(rec.Body.Bytes(), &created); err != nil || created.Data.ID == 0 {
+		t.Fatalf("create body %s: %v", rec.Body.String(), err)
+	}
+	slug := created.Data.Slug
+	recv.expectOnePurge(t, "create", "post", slug)
+
+	itemPath := fmt.Sprintf("/_journal/api/v1/posts/%d", created.Data.ID)
+	env.expect(t, http.StatusOK, http.MethodPut, itemPath, token, map[string]any{"content": "After"})
+	recv.expectOnePurge(t, "update", "post", slug)
+
+	env.expect(t, http.StatusOK, http.MethodDelete, itemPath, token, nil)
+	recv.expectOnePurge(t, "delete", "post", slug)
+}