Don't just store the id in the metadata but a JSON object with
the node name. This makes it possible to easily introspect the
metadata and also extend the metadata with more fields later.
Instead of matching the metadata id to the global ids we now
have to match it against the name.
The session manager might be configured without metadata support
so check this before attempting to use the metadata. It's not
really a problem because the default sink/source can only be
changed with the pulseaudio API, which activates metadata.
The prefix was used to filter the properties when loading and
saving but since the conversion to the core provided functions, this
feature is not longer available.
It's not exactly a problem, we could implement the filtering ourselves
afterwards but there is little point because we just ignore the unknown
items and never write invalid items.
Use separate metadata keys for the current effective default nodes
(default.*), and user-configured ones (default.configured.*).
default-nodes saves and restores the configured ones, and policy-node
keeps the effective ones up to date.
For pipewire users, the effective default values should be considered
read-only, as changing them will not have an effect. To avoid
confusion, policy-nodes will reset their values back immediately if they
are changed.
Save settings as jason and use a small json compatible tokenizer to
load settings instead of our own less flexible format.
Save settings with a prefix and filter out entries without prefix
Listen for changes in restore.stream metadata and update properties.
