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/unverified_users_and_reregistration_test.go

@@ -156,7 +156,7 @@ func newUnverifiedRegistrationRouter(userRepo *mockUserRepo, token *jwtauth.JWTA
 		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,
 	)