Description of problem:

The RBAC backend plugin fails to start with Backstage 1.47.x due to a breaking change in @backstage/backend-defaults@0.15.0 where the FetchUrlReader constructor was made private.

Prerequisites (if any, like setup, operators/versions):

Steps to Reproduce

 # <steps>

Actual results:

TypeError: Cannot read properties of undefined (reading 'predicate')                                                                                                                                             
  at new FetchUrlReader (.../node_modules/@backstage-community/plugin-rbac-backend/node_modules/@backstage/backend-defaults/src/entrypoints/urlReader/lib/FetchUrlReader.ts:135:31)                            
  at permissionFactory (.../node_modules/@backstage-community/plugin-rbac-backend/src/service/plugin-endpoints.ts:125:23)  

Expected results:

The RBAC backend plugin should start successfully with Backstage 1.47.x.

Reproducibility (Always/Intermittent/Only Once):

Build Details:

Additional info (Such as Logs, Screenshots, etc):

https://github.com/backstage/community-plugins/issues/7362