* Fix handling of attachments in JSON RPC
It turns out that using a custom serializer on an
input stream did not work well. For one the stream seems
to be getting closed before the JSON gets written. But
also the method for writing it was throwing an
UnsupportedOperationException further down in Jackson.
The above simplifies the matter by simply outputting the
Base64 string first and then setting it on the model.
* Add missing files to attachment fix
Co-authored-by: cedb <cedb@keylimebox.org>
* Add command to get an attachment
* Refactor retrieving of attachments to use StreamDetails
* Refactor AttachmentCommand to GetAttachmentCommand
* Minor improvements to GetAttachmentCommand
* Use JSON serializer to serialize binary data
Serializing the stream is better for memory handling than
loading the whole thing into the file.
* Clean up unneeded class
* Added command to doc
Co-authored-by: cedb <cedb@keylimebox.org>
