API: return resource ID for auth key creation, folder permissions update and user invite complete endpoints (#27419)

* API: add ID to auth key and folder endpoints

* API: add test for folder permissions update

* API: add created user id for /invite/complete endpoint

pkg/api/org_invite.go

@@ -211,7 +211,10 @@ func (hs *HTTPServer) CompleteInvite(c *models.ReqContext, completeInvite dtos.C
 	metrics.MApiUserSignUpCompleted.Inc()
 	metrics.MApiUserSignUpInvite.Inc()
 
-	return Success("User created and logged in")
+	return JSON(200, util.DynMap{
+		"message": "User created and logged in",
+		"id":      user.Id,
+	})
 }
 
 func updateTempUserStatus(code string, status models.TempUserStatus) (bool, Response) {