backend-app-api: move listPublicServiceKeys to authService

Co-authored-by: Patrik Oldsberg <poldsberg@gmail.com>
Signed-off-by: Vincenzo Scamporlino <vincenzos@spotify.com>

packages/backend-plugin-api/src/services/definitions/AuthService.ts

@@ -14,6 +14,8 @@
  * limitations under the License.
  */
 
+import { JsonObject } from '@backstage/types';
+
 /**
  * @public
  */
@@ -91,4 +93,8 @@ export interface AuthService {
   getLimitedUserToken(
     credentials: BackstageCredentials<BackstageUserPrincipal>,
   ): Promise<{ token: string; expiresAt: Date }>;
+
+  listPublicServiceKeys(): Promise<{
+    keys: JsonObject[];
+  }>;
 }