User Reader Settings
Per-user, per-series reader overrides
Get the authenticated user's reader overrides for a series
The response is sparse: a field is absent when the user has not overridden
Clear all of the authenticated user's reader overrides for a series
The series inherits fully again: series metadata, then the library default.
Update the authenticated user's reader overrides for a series
Ordinary PATCH semantics, per field: absent leaves the setting alone, an