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/database/models/mongo/User.js

@@ -1,135 +0,0 @@
-var mongoose = require('mongoose');
-var uniqueValidator = require('mongoose-unique-validator');
-var crypto = require('crypto');
-const { v4: uuidv4 } = require('uuid');
-var jwt = require('jsonwebtoken'),
-    config = require('../../../config');
-
-var UserSchema = new mongoose.Schema({
-    //_id: { type: String, default: uuidv4() },
-    _id: { type: mongoose.Schema.Types.UUID },
-    email: { type: String, lowercase: true, unique: true, required: [true, "email can't be blank"], match: [/\S+@\S+\.\S+/, 'is invalid'], index: true },
-    username: { type: String, lowercase: true, unique: true, required: [true, "username can't be blank"], match: [/^[a-zA-Z0-9_]+$/, 'is invalid'], index: true },
-    role: String,
-    firstname: { type: String, required: [true, "firstname can't be blank"] },
-    lastname: { type: String, required: [true, "lastname can't be blank"] },
-    phone: String,
-    licence: Number,
-    poids: Number,
-    image: String,
-    bg_image: String,
-    favorites: [{ type: mongoose.Schema.Types.ObjectId, ref: 'Product' }],
-    following: [{ type: mongoose.Schema.Types.UUID, ref: 'User' }],
-    hash: String,
-    salt: String
-}, { timestamps: true, toJSON: { virtuals: true } });
-
-UserSchema.plugin(uniqueValidator, { message: 'is already taken.' });
-
-UserSchema.methods.validPassword = function (password) {
-    let hash = crypto.pbkdf2Sync(password, this.salt, 10000, 512, 'sha512').toString('hex');
-    return this.hash === hash;
-};
-
-UserSchema.methods.setPassword = function (password) {
-    this.salt = crypto.randomBytes(16).toString('hex');
-    this.hash = crypto.pbkdf2Sync(password, this.salt, 10000, 512, 'sha512').toString('hex');
-};
-
-UserSchema.methods.generateJWT = function () {
-    var today = new Date();
-    var exp = new Date(today.getTime() + (config.session_lifetime * 1000));
-
-    return jwt.sign({
-        id: this._id,
-        username: this.username,
-        exp: parseInt(exp.getTime() / 1000)
-    }, config.secret, { algorithm: 'HS256' });
-};
-
-UserSchema.methods.toAuthJSON = function () {
-    return {
-        id: this._id,
-        email: this.email,
-        role: this.role,
-        token: this.generateJWT(),
-        firstname: this.firstname,
-        lastname: this.lastname,
-        phone: this.phone,
-        licence: this.licence,
-        poids: this.poids,
-        username: this.username,
-        image: this.image || '/assets/images/avatars/default.jpg',
-        bg_image: this.bg_image || '/assets/images/users/bg_user.jpg'
-    };
-};
-
-UserSchema.methods.toJSONFor = function () {
-    return {
-        email: this.email,
-        role: this.role,
-        firstname: this.firstname,
-        lastname: this.lastname,
-        phone: this.phone,
-        licence: this.licence,
-        poids: this.poids,
-        username: this.username,
-        image: this.image || '/assets/images/avatars/default.jpg',
-        bg_image: this.bg_image || '/assets/images/users/bg_user.jpg'
-    };
-};
-
-UserSchema.methods.toProfileJSONFor = function (user) {
-    return {
-        email: this.email,
-        firstname: this.firstname,
-        lastname: this.lastname,
-        phone: this.phone,
-        licence: this.licence,
-        poids: this.poids,
-        username: this.username,
-        image: this.image || '/assets/images/avatars/default.jpg',
-        bg_image: this.bg_image || '/assets/images/users/bg_user.jpg',
-        following: user ? user.isFollowing(this._id) : false
-    };
-};
-
-UserSchema.methods.favorite = function (id) {
-    if (this.favorites.indexOf(id) === -1) {
-        this.favorites.push(id);
-    }
-
-    return this.save();
-};
-
-UserSchema.methods.unfavorite = function (id) {
-    this.favorites.remove(id);
-    return this.save();
-};
-
-UserSchema.methods.isFavorite = function (id) {
-    return this.favorites.some(function (favoriteId) {
-        return favoriteId.toString() === id.toString();
-    });
-};
-
-UserSchema.methods.follow = function (id) {
-    if (this.following.indexOf(id) === -1) {
-        this.following.push(id);
-    }
-
-    return this.save();
-};
-
-UserSchema.methods.unfollow = function (id) {
-    this.following.remove(id);
-    return this.save();
-};
-
-UserSchema.methods.isFollowing = function (id) {
-    return this.following.some(function (followId) {
-        return followId.toString() === id.toString();
-    });
-};
-
-mongoose.model('User', UserSchema);