Remove some circular references
Merge pull request #964 from romainneutron/circular-refs-1

[3.9] Remove some circular references
Migrate demand table to doctrine entity && refactor registration API
Fix neutron's comment
Fix tests, CS && typo
Rename RegistrationManager to RegistrationManipulator
Adressed Neutron's comments
Refactor && Typo && Use plain objects as function parameters instead of ids
Fix tests & rename RegistrationDemandMigration class
CS fixer
Addressed neutron's comments
Fix unit tests