Issue270 Fix (#289)

* Add branching section into CONTRIBUTING.md - Merge in develop (#286)

* Clean up (#282)

* removed hardcoded URL

* Removed unnecessary endpoint

* Add illustrations for feature and hotfix branches to use in CONTRIBUTING.md

Image source: https://www.atlassian.com/git/tutorials/comparing-workflows/gitflow-workflow. License checked

* Add branching section into to use in CONTRIBUTING.md

Describe the use of Gitflow in SonarQuest

Co-authored-by: Michael Landreh <[email protected]>

* Fix #270 - Password is returned (#287)

* Change input color of login input fields

* Add necessary fields into UserDto

* Fix Nullpointer Exceptions in world service

This occurs when a world should be found by an id that is null

* Change return type of 'getUser' and 'users' into UserDto

* Adjust getUser to be null safe

Co-authored-by: Nils <[email protected]>
Co-authored-by: Michael Landreh <[email protected]>