+- Expiring/ephemeral activites. All activities can have expires_at value set, which controls when they should be deleted automatically.
+- Mastodon API: in post_status, the expires_in parameter lets you set the number of seconds until an activity expires. It must be at least one hour.
+- Mastodon API: all status JSON responses contain a `pleroma.expires_at` item which states when an activity will expire. The value is only shown to the user who created the activity. To everyone else it's empty.
+- Configuration: `ActivityExpiration.enabled` controls whether expired activites will get deleted at the appropriate time. Enabled by default.
+- Conversations: Add Pleroma-specific conversation endpoints and status posting extensions. Run the `bump_all_conversations` task again to create the necessary data.
+- **Breaking:** MRF describe API, which adds support for exposing configuration information about MRF policies to NodeInfo.
+ Custom modules will need to be updated by adding, at the very least, `def describe, do: {:ok, %{}}` to the MRF policy modules.