test: add tests for id.bund.de reply channel and applicationId in additional reference info (planning#2223)

refactor: adjust models, add id.bund.de als reply channel and id.bund.de mailbox as additional reference (planning#2223)

test: add tests for id.bund.de reply channel and applicationId in additional reference info (planning#2223)

refactor: adjust models, add id.bund.de als reply channel and id.bund.de mailbox as additional reference (planning#2223)

refactor: only delete incoming and outgoing files and folders created by the sdk within the attachment storage base folder (planning#1522)

refactor: remove input-stream option since it leads to unwanted behaviour creating files within the object without using the directory resolver   (planning#1522)

refactor: add chunk size as separate object to simplify mapping and representation of units mapping  (planning#1522)