The STRICT flag makes _serialize() nullable which is an API break for bindings. Forbid it and add _serialize_full() that accepts it and is properly annotated. Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/5829>
Forward custom meta to peer ipcsrc elements Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/6006>