refac: register only open while no verified acc exists, enforced by a use case rather than handler & sends verification email whose link uses the conf pub URL whose code expires after 2h

test/not_found_errors_test.go

@@ -136,7 +136,7 @@ func newNotFoundErrorsRouter(articleRepo *mockArticleRepo, userRepo *mockUserRep
 		token,
 		useCases.NewGetUserUseCase(userRepo),
 		useCases.NewListUsersUseCase(userRepo),
-		useCases.NewCreateUserUseCase(userRepo, hasher),
+		useCases.NewCreateUserUseCase(userRepo, hasher, newMockMailRepo(), "https://cms.example.com"),
 		useCases.NewAuthenticateUserUseCase(userRepo, hasher),
 		true,
 	)