Add support for Studio Drafts in API and Backend

Describe the feature you’d like

Please implement support for studio drafts in the stash-box backend and API.

Currently, users can submit drafts to create or update scenes and performers directly via the API, which are then held in a temporary queue for moderator approval. However, there is no system available for studios.

This backend addition is a hard prerequisite before StashApp can implement a “Submit to Stash-Box” button on local studio details pages.

Describe the benefits this would bring to existing users

According to the official StashDB curation guidelines, scenes submitted to the database must be linked to a studio.

Currently, if a user wants to submit a new scene but the associated studio does not yet exist on StashDB, they have to manually pivot away from StashApp, open StashDB in a browser, create the studio draft there, wait/link it, and then proceed.

Is there an existing way to achieve this goal?

Not to my knowledge.

Additional context

This issue serves as the backend dependency for the corresponding StashApp frontend proposal: