message: auth-backend: add not found error if provider is not found
diff: @@ -22,6 +22,7 @@ import { Logger } from 'winston';
  import { createAuthProviderRouter } from '../providers';
  import { Config } from '@backstage/config';
  import { DatabaseKeyStore, TokenFactory, createOidcRouter } from '../identity';
  +import { NotFoundError } from '@backstage/backend-common';
  export interface RouterOptions {
  logger: Logger;
  @@ -88,5 +89,10 @@ export async function createRouter(
  }),
  );
  + router.use('/:provider/', req => {
  + const { provider } = req.params;
  + throw new NotFoundError(`No auth provider registered for '${provider}'`);
  + });
  +
  return router;
  }
  