Add local user erasure requests

changelogs/client_server/newsfragments/1730.feature

@@ -0,0 +1 @@
+Add local erasure requests, as per [MSC4025](https://github.com/matrix-org/matrix-spec-proposals/pull/4025).

data/api/client-server/registration.yaml

@@ -614,6 +614,26 @@ paths:
                     it must return an `id_server_unbind_result` of
                     `no-support`.
                   example: example.org
+                erase:
+                  x-addedInMatrixVersion: "1.10"
+                  type: boolean
+                  description: |-
+                    Whether the user would like their content to be erased as
+                    much as possible from the server.
+
+                    Erasure means that any users (or servers) which join the
+                    room after the erasure request are served redacted copies of
+                    the events sent by this account. Users which had visibility
+                    on those events prior to the erasure are still able to see
+                    unredacted copies. No redactions are sent and the erasure
+                    request is not shared over federation, so other servers
+                    might still serve unredacted copies.
+
+                    The server should additionally erase any non-event data
+                    associated with the user, such as [account data](/client-server-api/#client-config)
+                    and [contact 3PIDs](/client-server-api/#adding-account-administrative-contact-information).
+
+                    Defaults to `false` if not present.
         required: true
       responses:
         "200":