Refactoring validation middleware

Created by: Tirokk

Authored by roschaefer May 10, 2019 Merged May 14, 2019

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Pullrequest

Two things:

• Fix UpdateUser test block (was not testing anything).
• Put all validations in one place

@mattwr18 @ulfgebhardt please read my commit messages in this PR.

Issues

This is a follow-up on #478

Checklist

• None

How2Test

• None

Todo

• None