add-endpoint

Prompt file imported from oleksa-karpenko/LLeague (.github/prompts/add-endpoint.prompt.md). Copyright stays with the author.

Add a new API endpoint to the backend, respecting the Clean Architecture layering.

Ask me for (or infer from context): the route, HTTP verb, request/response shape, and auth requirement.

Then implement, in this order:

1. DTOs — add request/response records to the appropriate Application/*Dtos.cs.
2. Application service — add the use-case method to the relevant Application/Services/*Service.cs (or create a new service + register it in Application/DependencyInjection.cs). Inject IAppDbContext. Throw domain exceptions (ValidationException, NotFoundException, UnauthorizedException, ConflictException) for error cases — never return status codes from the service.
3. Controller action — add a thin action to the matching Controllers/*Controller.cs: correct verb/route attribute, [Authorize]/[AllowAnonymous], and a one-line delegation to the service. No business logic, no try/catch (the middleware handles exceptions).
4. Tests — add xUnit integration tests ([Collection(ApiCollection.Name)], PostgresFixture) covering the happy path and the domain-exception paths. See .github/instructions/backend-tests.instructions.md.

Finally run cd backend && dotnet format LLeague.slnx && ./coverage.sh and confirm it's green.