Merges a directive into an existing Configuration JSON string, preserving every
other key. Returns the new JSON, or the original string when nothing changes
(so callers can cheaply detect no-op writes). Setting 'Sync' REMOVES the key
rather than storing the default.
Merges a directive into an existing Configuration JSON string, preserving every other key. Returns the new JSON, or the original string when nothing changes (so callers can cheaply detect no-op writes). Setting 'Sync' REMOVES the key rather than storing the default.