* Introduced `lyrics_synced` and `lyrics_unsynced` fields in the `Metadata` class.
* Updated the `Download` class to handle both synced and unsynced lyrics from the track.
* Enhanced metadata writing to include `UNSYNCEDLYRICS` in the tags.
* Introduced `MetadataTargetUPC` enum for target metadata tags.
* Added `METADATA_LOOKUP_UPC` dictionary for mapping file formats to UPC tags.
* Updated `Metadata` class to include `target_upc` for dynamic UPC tag assignment.
* Enhanced `Settings` class to allow configuration of `metadata_target_upc`.
This update introduces support for handling UPCs (Universal Product Codes) in metadata processing. It ensures that UPC information is extracted, stored, and written to the appropriate metadata tags for various formats.
- ✨ **Feature**: Adds UPC field to metadata handling.
- 🛠️ **Enhancement**: Updates metadata initialization to include UPC.
- 🗂️ **Tagging**: Implements UPC writing for supported file formats.
- ✅ **Compatibility**: Ensures proper handling when UPC is absent.
This improvement enhances metadata completeness and compatibility with systems requiring UPC data.
Robert Honz