Docs: Start sections about inbox and outbox

API.md

@@ -221,8 +221,126 @@ you've been given such a URI, the starting points for discovering objects are:
 - The user `Person` object, whose URI can be obtained from
   `/oauth/verify_credentials` as described above
 
+# The Person Object
+
+```json
+{
+    "id": "https://fig.fr33domlover.site/people/vDxKn",
+    "type": "Person",
+    "preferredUsername": "perelev",
+    "summary": "Cool person who makes cool stuff",
+    "inbox": "https://fig.fr33domlover.site/people/vDxKn/inbox",
+    "outbox": "https://fig.fr33domlover.site/people/vDxKn/outbox",
+    "followers": "https://fig.fr33domlover.site/people/vDxKn/followers",
+    "following": "https://fig.fr33domlover.site/people/vDxKn/following",
+    "sshKey": [
+        "https://fig.fr33domlover.site/people/vDxKn/ssh-keys/Pn9Yn"
+    ]
+}
+```
+
+# Receiving Messages
+
+Requests and event notifications are received as ActivityPub `Activity` objects
+in the Person's `inbox` collection. Currently push notifications aren't
+implemented, so client applications need to periodically GET the collection and
+detect whether new items have appeared at the top. The inbox is a (typically
+paged) reverse-chronologically `OrderedCollection` of `Activity` objects, as
+described in the ActivityPub specification.
+
+## Common properties
+
+These would appear in every actvity:
+
+- `id`: ID URI of the activity
+- `type`: One of the ActivityPub or ForgeFed activity types
+- `actor`: ID URI of the actor who published this activity
+
+These would appear in some activities:
+
+- `capability`: ID URI of a `Grant` activity serving as authorization
+- `fulfills`: If the activity was published by an automated process rather than
+  human command, these are ID URI(s) of the activities, to which the automated
+  process was reacting
+
+```json
+{
+    "id": "https://fig.fr33domlover.site/decks/W058b/outbox/nV34D",
+    "type": "Accept",
+    "actor": "https://fig.fr33domlover.site/decks/W058b",
+    "fulfills": [
+        "https://grape.fr33domlover.site/people/WZpnG/outbox/GQvnR"
+    ],
+    "object": "https://grape.fr33domlover.site/people/WZpnG/outbox/GQvnR"
+}
+```
+
+## Accept
+
+## Add
+
+## Apply
+
+## Create
+
+## Follow
+
+## Grant
+
+## Invite
+
+## Join
+
+## Offer
+
+## Push
+
+## Reject
+
+## Remove
+
+## Resolve
+
+## Revoke
+
+## Undo
+
 # Publishing and Manipulating Objects
 
 All object manipulation in Vervis is done using the ActivityPub C2S API, i.e.
-by POSTing `Activity` objects to the user's `outbox`. A list of supported
-activities will soon be added here and/or in the ForgeFed specification.
+by POSTing `Activity` objects to the user's `outbox`.
+
+To determine the outbox URI, you can HTTP GET the Person object as mentioned
+above, and grab the URI specified by its `outbox` field.
+
+## Common properties
+
+There are properties you'd often specify in the `Activity` object, that aren't
+specific to any activity type.
+
+- `type`: `Activity`
+- `actor`: URI of the person actor
+- `capability`: URI of a `Grant` activity you've received, as authorization for
+  the action you're requesting
+- `to`, `cc`, `bto`, `bcc`: Audience, i.e. list of URIs of actors and actor
+  collections
+
+## Accept
+
+## Add
+
+## Create
+
+## Follow
+
+## Invite
+
+## Join
+
+## Offer
+
+## Remove
+
+## Resolve
+
+## Undo