docs: sso.update_profile_information also supports synchronising the picture (avatar) claim

[micolous]

matrix-org/synapse#13917 added support for synchronising the user's avatar based on an OIDC picture claim.

It appears that this can be automatically synchronised on every login when sso.update_profile_information = true:

synapse/synapse/handlers/sso.py

Lines 515 to 531 in 2ce7a1e

	elif self._sso_update_profile_information:
	attributes = await self._call_attribute_mapper(sso_to_matrix_id_mapper)
	if attributes.display_name:
	user_id_obj = UserID.from_string(user_id)
	profile_display_name = await self._profile_handler.get_displayname(
	user_id_obj
	)
	if profile_display_name != attributes.display_name:
	requester = create_requester(
	user_id,
	authenticated_entity=user_id,
	)
	await self._profile_handler.set_displayname(
	user_id_obj, requester, attributes.display_name, True
	)
	if attributes.picture:
	await self.set_avatar(user_id, attributes.picture)

However, the update_profile_information docs state that only "displayname" is supported:

synapse/docs/usage/configuration/config_documentation.md

Lines 3680 to 3681 in 2ce7a1e

	* `update_profile_information`: Use this setting to keep a user's profile fields in sync with information from
	the identity provider. Currently only syncing the displayname is supported. Fields

This should mention that avatars are also supported.

[sandhose]

Good catch! The profile picture claim import has a few caveats, like the fact that it only really work in non-workerized deployments, and doesn't work with external media repositories, which might be why this has been forgotten in the docs.

Nonetheless, this should be updated, so feel free to open a PR to fix this!