Make verifyUserRelations() more robust

[mcitdev]

Description

Refactoring the verifyUserRelations function to :

• fix the app crash when the "accessTokens" relation is not correctly set up
• use more accurate condition in the first if statement
• prevent the redundant test of "hasManyTokens" in the function

See also #3934

[slnode]

Can one of the admins verify this patch? To accept patch and trigger a build add comment ".ok\W+to\W+test."

[bajtos]

@slnode test please

[bajtos]

Thank you @mcitdev for the pull request. The code changes looks good 👍 The commit history was a bit of a mess, I cleaned it up for you and rebased your patch on top of the latest master. Let's wait for CI results before landing.

Because you send the PR from your master branch, you will need a bit of cleanup work on your side to make your master branch up to date with our master branch (the upstream).

1. If you don't have strongloop's repository configured as an upstream remote yet:

   $ git remote add upstream https://github.com/strongloop/loopback
   

2. Fetch the latest updates from upstream:

   $ git fetch upstream
   

3. Hard-reset your master to upstream:

   $ git checkout master
   $ git reset --hard upstream/master
   

4. Force-push your changes back to GitHub

   $ git push -f
   

In the future, please create a new feature branch for each pull request. I recommend the following guide for step-by-step instructions showing the recommended contribution workflow: https://www.nearform.com/blog/first-time-with-open-source/

[bajtos]

Landed 🎉 Thank you for the contribution ❤️

[mcitdev]

I confess that I learned lot about git stuff from you, Thanks @bajtos