explore - Deprecated legacy backend (#2047)

Signed-off-by: Andre Wanlin <awanlin@spotify.com>

workspaces/explore/.changeset/lemon-elephants-provide.md

@@ -0,0 +1,5 @@
+---
+'@backstage-community/plugin-explore-backend': patch
+---
+
+Deprecated `createRouter` and its router options in favour of the new backend system.

workspaces/explore/plugins/explore-backend/report.api.md

@@ -12,7 +12,7 @@ import { GetExploreToolsRequest } from '@backstage-community/plugin-explore-comm
 import { GetExploreToolsResponse } from '@backstage-community/plugin-explore-common';
 import { LoggerService } from '@backstage/backend-plugin-api';
 
-// @public (undocumented)
+// @public @deprecated (undocumented)
 export function createRouter(options: RouterOptions): Promise<express.Router>;
 
 // @public
@@ -22,7 +22,7 @@ export default explorePlugin;
 // @public @deprecated (undocumented)
 export type ExploreToolProvider = ExploreToolProvider_2;
 
-// @public (undocumented)
+// @public @deprecated (undocumented)
 export interface RouterOptions {
   // (undocumented)
   logger: LoggerService;

workspaces/explore/plugins/explore-backend/src/service/router.ts

@@ -22,6 +22,8 @@ import { LoggerService } from '@backstage/backend-plugin-api';
 import { ExploreToolProvider } from '@backstage-community/plugin-explore-node';
 
 /**
+ * @deprecated Please migrate to the new backend system as this will be removed in the future.
+ *
  * @public
  */
 export interface RouterOptions {
@@ -30,6 +32,8 @@ export interface RouterOptions {
 }
 
 /**
+ * @deprecated Please migrate to the new backend system as this will be removed in the future.
+ *
  * @public
  */
 export async function createRouter(