Merge branch 'conversation-docs' into 'develop'

API Docs: Document conversation ids.

See merge request pleroma/pleroma!1701

docs/api/differences_in_mastoapi_responses.md

@@ -21,7 +21,8 @@ Adding the parameter `with_muted=true` to the timeline queries will also return
 Has these additional fields under the `pleroma` object:
 
 - `local`: true if the post was made on the local instance
-- `conversation_id`: the ID of the conversation the status is associated with (if any)
+- `conversation_id`: the ID of the AP context the status is associated with (if any)
+- `direct_conversation_id`: the ID of the Mastodon direct message conversation the status is associated with (if any)
 - `in_reply_to_account_acct`: the `acct` property of User entity for replied user (if any)
 - `content`: a map consisting of alternate representations of the `content` property with the key being it's mimetype. Currently the only alternate representation supported is `text/plain`
 - `spoiler_text`: a map consisting of alternate representations of the `spoiler_text` property with the key being it's mimetype. Currently the only alternate representation supported is `text/plain`