#414 Refactor api package structure

api/src/main/java/fitconnect/api/Sender.java

api/src/main/java/fitconnect/api/Subscriber.java

api/src/main/java/fitconnect/api/domain/auth/OAuthToken.java

...ct/api/domain/model/metadata/AdditionalReferenceInfo.java

.../api/domain/model/metadata/AuthenticationInformation.java

...itconnect/api/domain/model/metadata/ContentStructure.java

...n/java/fitconnect/api/domain/model/metadata/Metadata.java

...connect/api/domain/model/metadata/PaymentInformation.java

...tconnect/api/domain/model/metadata/PublicServiceType.java

...va/fitconnect/api/domain/model/metadata/ReplyChannel.java

...nect/api/domain/model/metadata/attachment/Attachment.java

...connect/api/domain/model/metadata/attachment/Purpose.java

...model/metadata/attachment/signature/EidasAdesProfile.java

...i/domain/model/metadata/attachment/signature/Hash__1.java

.../model/metadata/attachment/signature/SignatureFormat.java

...ain/model/metadata/attachment/signature/Signature__1.java

.../api/domain/model/metadata/attachment/signature/Type.java

.../java/fitconnect/api/domain/model/metadata/data/Data.java

...nect/api/domain/model/metadata/data/EidasAdesProfile.java

.../java/fitconnect/api/domain/model/metadata/data/Hash.java