Merge pull request 'OZG-3073-add-license' (#84) from OZG-3073-add-license into release

mail-service/pom.xml

...vsh/ozg/mail/attributes/ClientAttributeRemoteService.java

.../de/itvsh/ozg/mail/attributes/ClientAttributeService.java

...itvsh/ozg/mail/attributes/ClientAttributeTestFactory.java

...sh/ozg/mail/common/errorhandling/FunctionalException.java

...vsh/ozg/mail/common/errorhandling/TechnicalException.java

...mmon/grpc/NachrichtenCallContextAttachingInterceptor.java

...e/src/main/java/de/itvsh/ozg/mail/email/EMailService.java

...c/main/java/de/itvsh/ozg/mail/email/EmailGrpcService.java

.../src/main/java/de/itvsh/ozg/mail/email/MailRecipient.java

...main/java/de/itvsh/ozg/mail/email/MailSendErrorEvent.java

...rc/main/java/de/itvsh/ozg/mail/email/MailSendRequest.java

.../src/main/java/de/itvsh/ozg/mail/email/MailSentEvent.java

...ce/src/main/java/de/itvsh/ozg/mail/email/MailService.java

...in/java/de/itvsh/ozg/mail/postfach/AttachmentService.java

...in/java/de/itvsh/ozg/mail/postfach/BinaryFileService.java

...vice/src/main/java/de/itvsh/ozg/mail/postfach/FileId.java

...ice/src/main/java/de/itvsh/ozg/mail/postfach/Message.java

...in/java/de/itvsh/ozg/mail/postfach/MessageAttachment.java

...itvsh/ozg/mail/postfach/MockOsiPostfachConfiguration.java