refactor(web,server): use feature flags for oauth (#3928)

* refactor: oauth to use feature flags

* chore: open api

* chore: e2e test for authorize endpoint

server/src/domain/auth/response-dto/oauth-config-response.dto.ts

@@ -5,3 +5,7 @@ export class OAuthConfigResponseDto {
   buttonText?: string;
   autoLaunch?: boolean;
 }
+
+export class OAuthAuthorizeResponseDto {
+  url!: string;
+}