Pass through guest_access_token to the email

res/invite_template_vector.eml

@@ -16,7 +16,7 @@ Hi,
 %(sender_display_name)s has invited you into a room %(bracketed_room_name)s on
 Vector. To join the conversation please follow the link below.
 
-https://vector.im/#/room/%(room_id)s?email=%(to)s&signurl=https%%3A%%2F%%2Fvector.im%%2F_matrix%%2Fidentity%%2Fapi%%2Fv1%%2Fsign-ed25519%%3Ftoken%%3D%(token)s%%26private_key%%3D%(ephemeral_private_key)s&room_name=%(room_name)s&room_avatar_url=%(room_avatar_url)s&inviter_name=%(sender_display_name)s
+https://vector.im/#/room/%(room_id)s?email=%(to)s&signurl=https%%3A%%2F%%2Fvector.im%%2F_matrix%%2Fidentity%%2Fapi%%2Fv1%%2Fsign-ed25519%%3Ftoken%%3D%(token)s%%26private_key%%3D%(ephemeral_private_key)s&room_name=%(room_name)s&room_avatar_url=%(room_avatar_url)s&inviter_name=%(sender_display_name)s&guest_access_token=%(guest_access_token)s
 
 Please note that you will need to use Chrome, Firefox or Safari.
 
@@ -62,7 +62,7 @@ Vector.</p>
 
 <p>
     <a
-    href="https://vector.im/#/room/%(room_id)s?email=%(to)s&signurl=https%%3A%%2F%%2Fvector.im%%2F_matrix%%2Fidentity%%2Fapi%%2Fv1%%2Fsign-ed25519%%3Ftoken%%3D%(token)s%%26private_key%%3D%(ephemeral_private_key)s&room_name=%(room_name)s&room_avatar_url=%(room_avatar_url)s&inviter_name=%(sender_display_name)s">Join the conversation.</a>
+    href="https://vector.im/#/room/%(room_id)s?email=%(to)s&signurl=https%%3A%%2F%%2Fvector.im%%2F_matrix%%2Fidentity%%2Fapi%%2Fv1%%2Fsign-ed25519%%3Ftoken%%3D%(token)s%%26private_key%%3D%(ephemeral_private_key)s&room_name=%(room_name)s&room_avatar_url=%(room_avatar_url)s&inviter_name=%(sender_display_name)s&guest_access_token=%(guest_access_token)s">Join the conversation.</a>
 </p>
 
 <p>Please note that you will need to use Chrome, Firefox or Safari.</p>

sydent/http/servlets/store_invite_servlet.py

@@ -86,6 +86,7 @@ class StoreInviteServlet(Resource):
             'bracketed_room_name',
             'room_avatar_url',
             'sender_display_name',
+            'guest_access_token',
         ]
         for k in required:
             substitutions.setdefault(k, '')