Merge branch 'feature_Upgrade-to-TYPO3-10' into 'master'

Classes/Command/SendMailCommandController.php

Classes/Controller/ConfigurationController.php

Classes/Controller/LayoutController.php

Classes/Controller/MailController.php

Classes/Controller/NewsletterController.php

Classes/Controller/QueueController.php

Classes/Domain/Repository/AbstractRepository.php

Classes/Domain/Repository/FrontendUserGroupRepository.php

Classes/Domain/Repository/LayoutRepository.php

Classes/Domain/Repository/MailRepository.php

Classes/Domain/Repository/TemplateRepository.php

Classes/Finisher/Forms/FormsFinisher.php

Classes/Service/BackendService.php

Classes/Service/MailTemplateService.php

Classes/Service/RegisterService.php

Classes/Service/TypoScriptSettingsService.php

Classes/Updates/MigrateData.php

Classes/Updates/MigrateSchedulerTasks.php

Classes/Updates/UpdateGermanAsDefault.php

Classes/Updates/UpdateLanguages.php