Feat/service testing

See merge request !1

# Conflicts:
#   sth-backend/src/test/java/hdm/mi/sthbackend/serviceTests/FillBracketRandomTest.java
#   sth-frontend/src/utils/router.jsx

21.01.2024 - changes to Landingpage, added Back Button for Register and Login Page, various fixing from Code #12 #28 #30

20.01.2024 - added tests addPlayerToTeam_PlayerAddedSuccessfully, removePlayerFromTeam_PlayerRemovedSuccessfully, createAndAddTeamToTournament_TeamCreatedAndAddedSuccessfully, deleteAndRemoveTeamFromTournament_TeamDeletedAndRemovedSuccessfully #27

Merge branch 'feat/service-testing' of gitlab.mi.hdm-stuttgart.de:ss576/student-tournament-hub into feat/service-testing

21.01.2024 - added EmailContext Hook, changes to Header on Landingpage, added Navbar Links to Register and Login Routes, added Feature to enter Email from Landingpage to Register Page #12 #28 #30

20.01.2024 - updatet createTournamentTest to createTournament_TournamentInsertedSuccessfully and createTournament_TournamentInsertedSuccessfully works now #27

Merge branch 'feat/service-testing' of gitlab.mi.hdm-stuttgart.de:ss576/student-tournament-hub into feat/service-testing

20.01.2024 - updatet the test assignTeamToMatch_TeamAssignedSuccessfully and added assignTeamToMatch_MatchIdNotFoundException() and add UpdatePlayerName_TournamentIdNotFoundException  #27

20.01.2024 - deleted testFindPlayerById test and added updatePlayerName_PlayerNameUpdatedSuccessfully and testUpdatePlayerName_PlayerIdNotFoundException   #27