Moving from monolith/anemic to hexagonal/cqrs

[Sch3lp]

• [x] Copied effit-backend to effit-cqrs-backend so I can continuously refer to both architectures on stream.
• [x] introduce hexagonal just as packages first
• [x] extract domain from effit-backend as is
• [ ] introduce mapping stuff between future module dependencies
  • [x] move to using queries
    • [x] ChallengeController
    • [x] CompetitionController
  • [x] move to using commands
    • [x] CompetitionController
    • [x] ChallengeController
  • [x] remove findOrThrow duplication in CompetitionCommandHandlers (see comment)
  • [ ] clean up RestApiExposed interface usage from Core domain objects (should have been moved to the adapter-ui module)
  • [ ] implement command execution as applying commands to aggregates instead of logic in commandhandlers
• [ ] extract modules out of packages
• [ ] try to get rid of H2 dependency (see where it breaks if I do)
• [ ] get rid of hibernate and replace with something else (let's try spring data jdbc)

Check out the module dependency diagram:

[Sch3lp]

This is probably going to end up in all CompetitionCommandHandlers:

    private fun findCompetitionOrThrow(competitionId: CompetitionId): Competition {
        return queryExecutor.execute(FindCompetition(competitionId))
                ?: throw EntityNotFoundDomainRuntimeException("Competition with id ${competitionId.id} not found")
    }

So find a way to remove that duplication when it happens!