fix(swagger): swagger docs for http status code 409 [EE-5767] (#11535)

api/http/handler/stacks/create_compose_stack.go

@@ -229,6 +229,7 @@ func (payload *composeStackFromGitRepositoryPayload) Validate(r *http.Request) e
 // @param body body composeStackFromGitRepositoryPayload true "stack config"
 // @success 200 {object} portainer.Stack
 // @failure 400 "Invalid request"
+// @failure 409 "Stack name or webhook ID already exists"
 // @failure 500 "Server error"
 // @router /stacks/create/standalone/repository [post]
 func (handler *Handler) createComposeStackFromGitRepository(w http.ResponseWriter, r *http.Request, endpoint *portainer.Endpoint, userID portainer.UserID) *httperror.HandlerError {