beginning of the work on the email attachment display feature -- new callback for event providers to give extra info -- attachment content type+contents for emails. First rough start, tests don't compile
now the discriminator for the new callback can be any json-serializable type decided by the provider, not simply String
now at least it builds
work towards serving getExtraData result through http
work on String, though it's questionnable whether it is actually better
had the wrong header name for message id, so it could not work. also now decode the section content also instead of base64 for binary
generate in the display for emails raw links to download the attachments
only display attachments in the attachments links (not the main section for instance)
display the attachment name
nicer looking attachment display