GitLab

olm_import_inbound_group_session, which reads the format written by
olm_export_inbound_group_session to initialise a group session.

A pair of functions which allow you to export the megolm keys for an inbound
group session, so that an application can save/restore them.

Applications can use the index to detect replays of the same message.

Add ed25519 keys to the inbound and outbound sessions, and use them to sign and
verify megolm messages.

We just stuff the ed25519 public key in alongside the megolm session key (and
add a version byte), to save adding more boilerplate to the JS/python/etc
layers.

Make names (of session_key and message_index) more consistent.

Use our own protobuf tags rather than trying to piggyback on the one-to-one
structure.

Includes creation of inbound sessions, etc