Move sliding sync url logic out of matrix-client.j2

roles/custom/matrix-base/defaults/main.yml

@@ -150,6 +150,12 @@ matrix_homeserver_container_url: ""
 # This likely gets overriden elsewhere.
 matrix_homeserver_container_federation_url: ""
 
+# Specifies the public url of the Sync v3 (sliding-sync) API.
+# This will be used to set the `org.matrix.msc3575.proxy` property in `/.well-known/matrix/client`.
+# Once the API is stabilized, this will no longer be required.
+# See MSC3575: https://github.com/matrix-org/matrix-spec-proposals/blob/kegan/sync-v3/proposals/3575-sync.md
+matrix_homeserver_sliding_sync_url: ""
+
 matrix_identity_server_url: ~
 
 matrix_integration_manager_rest_url: ~

roles/custom/matrix-base/templates/static-files/well-known/matrix-client.j2

@@ -26,13 +26,9 @@
 		"preferredDomain": {{ matrix_client_element_jitsi_preferred_domain|to_json }}
 	}
 	{% endif %}
-	{% if matrix_sliding_sync_enabled %},
+	{% if matrix_homeserver_sliding_sync_url %},
 	"org.matrix.msc3575.proxy": {
-		"url": "{{ matrix_sliding_sync_base_url }}"
-	}
- 	{% elif matrix_homeserver_implementation == 'conduit' %},
-	"org.matrix.msc3575.proxy": {
-		"url": "{{ matrix_homeserver_url }}"
+		"url": "{{ matrix_homeserver_sliding_sync_url }}"
 	}
 	{% endif %}
 	{% if matrix_client_element_location_sharing_enabled %},