- Added `full_metadata` handling to return only relationship fields when requested.
- Implemented `filter_node_hierarchy_by_access` for access control filtering
rel 476
- Implement Pubsub Extended Discovery, and Pydantic models to handle the data easily.
- `client.discoHandler` initialisation has been moved in `core.xmpp` at an earlier stage
of the workflow as it has to be initialised so XEP-0499 could remove the default disco
handler to handle disco itself.
- Removed `Disco handled` trigger point as it was not used.
rel 463
