Implement GenericErrorResponse interface for all errors returned from /v2

[manuelwedler]

In the API v2 design we created the GenericErrorResponse interface for all errors returned by the new API:

export interface GenericErrorResponse {
  customCode: ErrorCode;
  message: string;
  errorId: string;
}

We should make sure that all errors that are returned from the /v2 endpoints are following this format. For that, we can implement some middleware, e.g. use("/v2", errorHandlingMiddleware) that matches unknown / uncaught errors to the new interface. This should also catch the ones returned by safeHandler. We should also ensure that validation errors follow this format. We might need to adapt our genericErrorHandler from api v1.

We will also need to define the custom error codes.