WIP: make sure user_params[:external] is respected

What does this MR do?

There seems to be a bug:

I tried with the current master (Commit: 77b3a8b1) branch the following:

0. login with an site-admin
1. save an internal-email-pattern like tester\.com in the admin settings
2. go to admin/users/new and create a user with rr@tester.com, which unchecked the external checkbox like it should.
3. Hit button Create user
4. The user created has external set to true. I don't know yet why.

I debugged a bit with binding.pry:

So the user_params are correct, but the new user still has user.external set to true. Do you have any idea why this happens and do you also see this as another bug? (i.e. that's not the expected behaviour, right?)

What are the relevant issue numbers?

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.