Add AccountService and Repository

All api-calls, that are doing some kind of account manipulation like: changePW, linkSteam, changeEmail etc.
should be only accessed through a AccountService/Repo.
This would have multiple benefits.

1. auto refresh token if expired (via JavaApiService)
2. no old "request" style code
3. error-handling can be done at a single place
4. clear parameters and return values
5. they are reusable (saw some duplicated code)
6. less testing hassle with mocking http, the service could also be injected in the router/controller

A solution could look something like:
Old:

```JavaScript
request.post({
url: process.env.API_URL + '/users/changePassword',
headers: { Authorization: 'Bearer ' + req.requestContainer.get('UserService').getUser()?.oAuthPassport.token },
form: { currentPassword: oldPassword, newPassword }
}, function (err, res, body) {
if (err || res.statusCode !== 200) {
error.parseApiErrors(body, flash)
return overallRes.render('account/changePassword', { flash })
}

// Successfully reset password
flash.class = 'alert-success'
flash.messages = [{ msg: 'Your password was changed successfully. Please use the new password to log in!' }]
flash.type = 'Success!'

overallRes.render('account/changePassword', { flash })
})
```

new:
```JavaScript
accountService.changePassword(oldPassword, newPassword).then(() => {
res.render('account/changePassword', { success: true })
}).catch((apiError) => {
res.render('account/changePassword', { error: apiError })
})
```