Allow change of login casing

[vonagam]

Closes #662.

[Brutus5000]

This is part of the validations, as such it should be in the validateUsername method. newLogin.equalsIgnoreCase(oldLogin) could cause an early return there before calling userRepository.existsByLogin

Also your PR should add a unit test for this case.

[vonagam]

could cause an early return there before calling userRepository.existsByLogin

That's the point, if newLogin.equalsIgnoreCase(oldLogin) it means that it passes username rules and that existsByLogin will return true and cause false error raise, so it is ok to skip validateUsername call here.

All other calls to validateUsername do not deal with situations when a user already exists (and so no false errors from existsByLogin there).

Added the test. Have not run it though, not a java developer, so do not have an environment setup. If you want to move this logic to validateUsername with Optional second argument of an existing user, that makes sense too, close this PR in that case.

[Brutus5000]

Ah shame on me. I thought the CI passed but it was just Codacy. Well... we'll see if the test works on develop :D