Add requestToken endpoints

For password reset and 3pid adding

api/client-server/administrative_contact.yaml

@@ -119,3 +119,12 @@ paths:
               }
       tags:
         - User data
+  "/account/3pid/email/requestToken":
+    post:
+      summary: Requests a validation token be sent to the given email address
+      description: |-
+        Proxies the identity server API ``validate/email/requestToken``, but
+        first checks that the given email address is not already associated
+        with an account on this Home Server. This API should be used to request
+        validation tokens when adding an email address to an account. This API
+	behaves identically to `/register/email/requestToken`

api/client-server/registration.yaml

@@ -242,3 +242,16 @@ paths:
             "$ref": "definitions/error.yaml"
       tags:
         - User data
+  "/account/password/email/requestToken":
+    post:
+      summary: Requests a validation token be sent to the given email address
+      description: |-
+        Proxies the identity server API ``validate/email/requestToken``, but
+        first checks that the given email address is associated with an account
+        on this Home Server. This API should be used to request
+        validation tokens when authenticating for the
+        `account/password` endpoint. This API behaves identically to
+        `/register/email/requestToken` except that `M_THREEPID_NOT_FOUND` may be
+        returned if no account matching the given email address could be found.
+        The server may instead send an email to the given address prompting
+        the user to create an account. `M_THREEPID_IN_USE` may not be returned.

specification/client_server_api.rst

@@ -116,6 +116,9 @@ Some requests have unique error codes:
 :``M_THREEPID_IN_USE``:
   Sent when a threepid given to an API cannot be used because the same threepid is already in use.
 
+:``M_THREEPID_NOT_FOUND``:
+  Sent when a threepid given to an API cannot be used because no record matching the threepid was found
+
 :``M_SERVER_NOT_TRUSTED``:
   The client's request used a third party server, eg. ID server, that this server does not trust.