fix: add fallback icons for notifications (#17013)

Related: https://github.com/coder/internal/issues/522

coderd/inboxnotifications_internal_test.go

@@ -0,0 +1,51 @@
+package coderd
+
+import (
+	"testing"
+	"time"
+
+	"github.com/google/uuid"
+	"github.com/stretchr/testify/require"
+
+	"github.com/coder/coder/v2/coderd/notifications"
+	"github.com/coder/coder/v2/codersdk"
+)
+
+func TestInboxNotifications_ensureNotificationIcon(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name         string
+		icon         string
+		templateID   uuid.UUID
+		expectedIcon string
+	}{
+		{"WorkspaceCreated", "", notifications.TemplateWorkspaceCreated, codersdk.FallbackIconWorkspace},
+		{"UserAccountCreated", "", notifications.TemplateUserAccountCreated, codersdk.FallbackIconAccount},
+		{"TemplateDeleted", "", notifications.TemplateTemplateDeleted, codersdk.FallbackIconTemplate},
+		{"TestNotification", "", notifications.TemplateTestNotification, codersdk.FallbackIconOther},
+		{"TestExistingIcon", "https://cdn.coder.com/icon_notif.png", notifications.TemplateTemplateDeleted, "https://cdn.coder.com/icon_notif.png"},
+		{"UnknownTemplate", "", uuid.New(), codersdk.FallbackIconOther},
+	}
+
+	for _, tt := range tests {
+		tt := tt
+
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
+			notif := codersdk.InboxNotification{
+				ID:         uuid.New(),
+				UserID:     uuid.New(),
+				TemplateID: tt.templateID,
+				Title:      "notification title",
+				Content:    "notification content",
+				Icon:       tt.icon,
+				CreatedAt:  time.Now(),
+			}
+
+			notif = ensureNotificationIcon(notif)
+			require.Equal(t, tt.expectedIcon, notif.Icon)
+		})
+	}
+}