plugin invitation: pubsub invitations:

- new Pubsub invitation plugin, to have a generic way to manage invitation on Pubsub based
  features
- `invitePreflight` and `onInvitationPreflight` method can be implemented to customise
  invitation for a namespace
- refactored events invitations to use the new plugin
- a Pubsub invitation can now be for a whole node instead of a specific item
- if invitation is for a node, a namespace can be specified to indicate what this node is
  about. It is then added in `extra` data
- an element (domish.Element) can be added in `extra` data, it will then be added in the
  invitation
- some code modernisation

sat/plugins/plugin_exp_invitation_file.py

@@ -19,6 +19,7 @@
 from sat.core.i18n import _
 from sat.core.constants import Const as C
 from sat.core.log import getLogger
+from sat.core.xmpp import SatXMPPEntity
 from sat.tools.common import data_format
 from twisted.internet import defer
 from twisted.words.protocols.jabber import jid
@@ -69,7 +70,17 @@ class FileSharingInvitation:
                 extra=extra)
         )
 
-    def onInvitation(self, client, name, extra, service, repos_type, namespace, path):
+    def onInvitation(
+        self,
+        client: SatXMPPEntity,
+        namespace: str,
+        name: str,
+        extra: dict,
+        service: jid.JID,
+        repos_type: str,
+        sharing_ns: str,
+        path: str
+    ):
         if repos_type == "files":
             type_human = _("file sharing")
         elif repos_type == "photos":
@@ -81,11 +92,12 @@ class FileSharingInvitation:
             type_human = _("file sharing")
         log.info(_(
             '{profile} has received an invitation for a files repository ({type_human}) '
-            'with namespace {namespace!r} at path [{path}]').format(
-            profile=client.profile, type_human=type_human, namespace=namespace, path=path)
+            'with namespace {sharing_ns!r} at path [{path}]').format(
+            profile=client.profile, type_human=type_human, sharing_ns=sharing_ns,
+                path=path)
             )
         return defer.ensureDeferred(
             self.host.plugins['LIST_INTEREST'].registerFileSharing(
-                client, service, repos_type, namespace, path, name, extra
+                client, service, repos_type, sharing_ns, path, name, extra
             )
         )