[WP] Improve sync progress

[anamarijapapic]

No description provided.

[height]

This pull request has been linked to 2 tasks:

• T-380 [WP] separate sync progress messages into its own endpoint with pagination (unlink task)
• T-379 [WP] add model_id column to sync_progress table and count synced items by its distinct value (unlink task)

💡Tip: Add "Close T-380" to the pull request title or description, to a commit message, or in a comment to mark this task as "Done" when the pull request is merged.

[anteprimorac]

@anamarijapapic s ovim se netko tko već ima instaliran plugin neće moći migrirati na novu verziju jer dodajemo novu kolumnu koja je not null, a u bazi možda već postoje podaci u toj tablici