disable inviting new users to orgs if login form is disabled

pkg/api/login.go

@@ -94,6 +94,10 @@ func LoginApiPing(c *middleware.Context) {
 }
 
 func LoginPost(c *middleware.Context, cmd dtos.LoginCommand) Response {
+	if setting.DisableLoginForm {
+		return ApiError(401, "Login is disabled", nil)
+	}
+
 	authQuery := login.LoginUserQuery{
 		Username: cmd.User,
 		Password: cmd.Password,