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/qcm.routes.js

@@ -3,9 +3,9 @@ var router = require('express').Router(),
     Qcm = mongoose.model('Qcm'),
     QcmCategory = mongoose.model('QcmCategory'),
     QcmQuestion = mongoose.model('QcmQuestion'),
-    QcmChoice = mongoose.model('QcmChoice'),
-    User = mongoose.model('User');
+    QcmChoice = mongoose.model('QcmChoice');
 const auth = require('../../../middlewares/auth');
+const { UserService } = require('../../../services');
 
 // Preload qcm objects on routes with ':type'
 router.param('type', function (req, res, next, type) {
@@ -37,7 +37,7 @@ router.param('type', function (req, res, next, type) {
  */
 router.get('/', auth.required, function (req, res, next) {
     Promise.all([
-        req.payload ? User.findById(req.payload.id) : null
+        req.payload ? UserService.getUserById(req.payload.id) : null
     ]).then(function (results) {
         let user = results[0];
         if (!user) {
@@ -52,7 +52,7 @@ router.get('/', auth.required, function (req, res, next) {
  */
 router.get('/type/:type', auth.required, function (req, res, next) {
     Promise.all([
-        req.payload ? User.findById(req.payload.id) : null
+        req.payload ? UserService.getUserById(req.payload.id) : null
     ]).then(function (results) {
         let user = results[0];
         if (!user) {
@@ -67,14 +67,13 @@ router.get('/type/:type', auth.required, function (req, res, next) {
  */
 router.post('/choices/', auth.required, function (req, res, next) {
     Promise.all([
-        req.payload ? User.findById(req.payload.id) : null,
+        req.payload ? UserService.getUserById(req.payload.id) : null,
         QcmQuestion
             .findOne({num: req.body.question.num})
             .populate('choices')
             .exec()
     ]).then(async function (results) {
         const user = results[0];
-        //let numero = (results[1][0].numero + 1);
         if (!user) {
             return res.status(401).json({ errors: { "Unauthorized": "autentification requise" } });
         }
@@ -113,14 +112,13 @@ router.post('/choices/', auth.required, function (req, res, next) {
  */
 router.post('/questions/', auth.required, function (req, res, next) {
     Promise.all([
-        req.payload ? User.findById(req.payload.id) : null,
+        req.payload ? UserService.getUserById(req.payload.id) : null,
         QcmCategory
             .findOne({num: req.body.category.num})
             .populate('questions')
             .exec()
     ]).then(async function (results) {
         const user = results[0];
-        //let numero = (results[1][0].numero + 1);
         if (!user) {
             return res.status(401).json({ errors: { "Unauthorized": "autentification requise" } });
         }
@@ -154,4 +152,4 @@ router.post('/questions/', auth.required, function (req, res, next) {
     }).catch(next);
 });
 
-module.exports = router;
+module.exports = router;