Fix some deprecations and deprecate old backend system

As described here: backstage/community-plugins#1176

.changeset/cool-rockets-confess.md

@@ -0,0 +1,10 @@
+---
+'@spreadshirt/backstage-plugin-s3-viewer-backend': patch
+---
+
+Replace some deprecations caused by the removal of the backend-tasks plugin and deprecate old backend system.
+
+The old backend system calls will be completely removed in the next release, so
+none of the deprecations caused by these functions are going to be addressed.
+
+More info about this process [in this issue](https://github.com/backstage/community-plugins/issues/1176).

plugins/s3-viewer-backend/config.d.ts

@@ -1,4 +1,4 @@
-import { TaskScheduleDefinitionConfig } from '@backstage/backend-tasks';
+import { SchedulerServiceTaskScheduleDefinitionConfig } from '@backstage/backend-plugin-api';
 
 /** Configuration for the S3 Viewer plugin */
 export interface Config {
@@ -7,7 +7,9 @@ export interface Config {
      * If defined, it sets the schedule used to refresh the list of buckets
      * @visibility backend
      * */
-    bucketRefreshSchedule: TaskScheduleDefinitionConfig | undefined;
+    bucketRefreshSchedule:
+      | SchedulerServiceTaskScheduleDefinitionConfig
+      | undefined;
 
     /** @visibility backend */
     bucketLocatorMethods: Array<

plugins/s3-viewer-backend/src/run.ts

@@ -14,13 +14,13 @@
  * limitations under the License.
  */
 
-import { getRootLogger } from '@backstage/backend-common';
+import { mockServices } from '@backstage/backend-test-utils';
 import yn from 'yn';
 import { startStandaloneServer } from './service/standaloneServer';
 
 const port = process.env.PLUGIN_PORT ? Number(process.env.PLUGIN_PORT) : 7007;
 const enableCors = yn(process.env.PLUGIN_CORS, { default: false });
-const logger = getRootLogger();
+const logger = mockServices.logger.mock();
 
 startStandaloneServer({ port, enableCors, logger }).catch(err => {
   logger.error(err);

plugins/s3-viewer-backend/src/service/router.ts

@@ -45,6 +45,10 @@ export interface RouterOptions {
   httpAuth?: HttpAuthService;
 }
 
+/**
+ * @deprecated Use the new backend system instead
+ * @public
+ */
 export async function createRouter(
   options: RouterOptions,
 ): Promise<express.Router> {