refactor(skydive): replace MongoDB User with MySQL UserService

All skydive routes now fetch users via UserService (MySQL) instead of
mongoose.model('User'). Key changes:
- user._id.toString() → user.id (same UUID, different source)
- User.findOne({ username }) → UserService.getUserByUsername()
- /feed route migrated to async/await using UserService.getUserFollowed()
  to resolve the following list from the MySQL Follower table
- jump/file/application author set as user.id (UUID string) instead of
  the full Mongoose document
- jump.toJSONFor(null) — following field in responses is now always false
  until Jump model is migrated away from MongoDB User dependency
- user.controller: licence/poids/bg_image routed to SkydiverProfileService
  fixing the silent Sequelize save bug for those fields

src/routes/api/skydive/applications.routes.js

@@ -1,9 +1,9 @@
 var router = require('express').Router(),
     mongoose = require('mongoose'),
-    Application = mongoose.model('Application'),
-    User = mongoose.model('User');
+    Application = mongoose.model('Application');
 const auth = require('../../../middlewares/auth'),
     mailer = require('@sendgrid/mail');
+const { UserService } = require('../../../services');
 
 mailer.setApiKey(process.env.SENDGRID_API_KEY);
 
@@ -42,10 +42,10 @@ router.get('/', auth.required, function (req, res, next) {
     }
 
     Promise.all([
-        req.query.author ? User.findOne({ username: req.query.author }) : null
+        req.query.author ? UserService.getUserByUsername(req.query.author) : null
     ]).then(function (author) {
         if (author[0]) {
-            query.author = author[0]._id;
+            query.author = author[0].id;
         }
         return Promise.all([
             Application.find(query)
@@ -55,7 +55,7 @@ router.get('/', auth.required, function (req, res, next) {
                 .populate('author')
                 .exec(),
             Application.count(query).exec(),
-            req.payload ? User.findById(req.payload.id) : null
+            req.payload ? UserService.getUserById(req.payload.id) : null
         ]).then(function (results) {
             let applications = results[0];
             let applicationsCount = results[1];
@@ -76,7 +76,7 @@ router.get('/', auth.required, function (req, res, next) {
  */
 router.post('/', auth.required, function (req, res, next) {
     Promise.all([
-        User.findById(req.payload.id),
+        UserService.getUserById(req.payload.id),
         auth.generateAPIKey()
     ]).then(function (results) {
         let user = results[0];
@@ -85,7 +85,7 @@ router.post('/', auth.required, function (req, res, next) {
             return res.sendStatus(401).json({message: "Unauthorized - You are not allowed to access this resource."});
         }
         let application = new Application(req.body.application);
-        application.author = user;
+        application.author = user.id;
         application.apikey = keys.encrypted;
         application.maskedkey = keys.masked;
         return application.save().then(function () {
@@ -117,7 +117,7 @@ router.post('/', auth.required, function (req, res, next) {
  */
 router.get('/:application', auth.required, function (req, res, next) {
     Promise.all([
-        req.payload ? User.findById(req.payload.id) : null,
+        req.payload ? UserService.getUserById(req.payload.id) : null,
         req.application.populate('author')
     ]).then(function (results) {
         let user = results[0];
@@ -129,8 +129,9 @@ router.get('/:application', auth.required, function (req, res, next) {
  * update an application
  */
 router.put('/:application', auth.required, function (req, res, next) {
-    User.findById(req.payload.id).then(function (user) {
-        if (req.application.author._id.toString() === req.payload.id.toString()) {
+    UserService.getUserById(req.payload.id).then(function (user) {
+        const authorId = req.application.author?.id ?? req.application.author?.toString();
+        if (authorId === req.payload.id) {
             if (typeof req.body.application.title !== 'undefined') {
                 req.application.title = req.body.application.title;
             }
@@ -156,11 +157,12 @@ router.put('/:application', auth.required, function (req, res, next) {
  * delete an application
  */
 router.delete('/:application', auth.required, function (req, res, next) {
-    User.findById(req.payload.id).then(function (user) {
+    UserService.getUserById(req.payload.id).then(function (user) {
         if (!user) {
             return res.status(401).json({ errors: { "Unauthorized": "autentification requise" } });
         }
-        if (user.role == 'Admin' || req.application.author._id.toString() === req.payload.id.toString()) {
+        const authorId = req.application.author?.id ?? req.application.author?.toString();
+        if (user.role == 'Admin' || authorId === req.payload.id) {
             return req.application.remove().then(function () {
                 return res.json({ deleted: true });
             });