Move `invite_room_state` to the correct place in the client-server API

Fixes https://github.com/matrix-org/matrix-doc/issues/1350

event-schemas/examples/m.room.member#invite_room_state

@@ -5,6 +5,7 @@
     "avatar_url": "mxc://localhost/SEsfnsuifSDFSSEF#auto",
     "displayname": "Alice Margatroid"
   },
+  "unsigned": {
     "invite_room_state": [
       {
         "type": "m.room.name",
@@ -20,7 +21,8 @@
           "join_rule": "invite"
         }
       }
-  ],
+    ]
+  },
   "state_key": "@alice:localhost",
   "origin_server_ts": 1431961217939,
   "event_id": "$WLGTSEFSEF:localhost",

event-schemas/schema/m.room.member

@@ -18,7 +18,9 @@ description: |-
 
   The ``third_party_invite`` property will be set if this invite is an ``invite`` event and is the successor of an ``m.room.third_party_invite`` event, and absent otherwise.
 
-  This event may also include an ``invite_room_state`` key **outside the** ``content`` **key**. If present, this contains an array of ``StrippedState`` Events. These events provide information on a subset of state events such as the room name.
+  This event may also include an ``invite_room_state`` key inside the event's ``unsigned`` data.
+  If present, this contains an array of ``StrippedState`` Events. These events provide information
+  on a subset of state events such as the room name.
 properties:
   content:
     properties:
@@ -71,10 +73,11 @@ properties:
           - signed
         title: Invite
         type: object
-    required:
-      - membership
-    title: EventContent
+      unsigned:
         type: object
+        title: UnsignedData
+        description: Contains optional extra information about the event.
+        properties:
           invite_room_state:
             description: 'A subset of the state of the room at the time of the invite, if ``membership`` is ``invite``. Note that this state is informational, and SHOULD NOT be trusted; once the client has joined the room, it SHOULD fetch the live state from the server and discard the invite_room_state. Also, clients must not rely on any particular state being present here; they SHOULD behave properly (with possibly a degraded but not a broken experience) in the absence of any particular events here. If they are set on the room, at least the state for ``m.room.avatar``, ``m.room.canonical_alias``, ``m.room.join_rules``, and ``m.room.name`` SHOULD be included.'
             items:
@@ -97,6 +100,10 @@ properties:
               title: StrippedState
               type: object
             type: array
+    required:
+      - membership
+    title: EventContent
+    type: object
   state_key:
     description: The ``user_id`` this membership event relates to.
     type: string

scripts/templating/matrix_templates/units.py

@@ -875,15 +875,6 @@ class MatrixUnits(Units):
             Units.prop(json_schema, "properties/content")
         )
 
-        # This is horrible because we're special casing a key on m.room.member.
-        # We need to do this because we want to document a non-content object.
-        if schema["type"] == "m.room.member":
-            invite_room_state = get_tables_for_schema(
-                json_schema["properties"]["invite_room_state"]["items"],
-            )
-            schema["content_fields"].extend(invite_room_state)
-
-
         # grab msgtype if it is the right kind of event
         msgtype = Units.prop(
             json_schema, "properties/content/properties/msgtype/enum"