Migrations/Imports: ModulestoreSource listing API

[kdmccormick]

This REST API will be used by both the Course-to-Library Import UI and the Legacy Libraries Migration UI. They will need it in order to query whether a given course or library has been migrated and whether it has an authoritative migration.

Endpoint:

• GET /api/modulestore_migrator/v1/sources
  • Returns a paginated list of ModulestoreSources which the requester has Read access to.
  • Each object should include:
    • key (str): The source's LearningContextKey (CourseKey or legacy LibraryKey)
    • forwarded (str | null): If the source has been authoritatively migrated, the UUID of that ModulestoreMigration
    • migrations (list of str): List of ModulestoreMigration UUIDs for this source

Note: The requester will use the UUIDs returned by this API in order to query the existing /api/modulestore_migrator/v1/migrations/<uuid> API.

[kdmccormick]

@cmltaWt0 @bradenmacdonald , in addition the /api/modulestore_migrator/v1/migrations API which Max's current PR will add, this ticket describes one additional API which will be needed in order to implement migrations on the Legacy Libraries page.

[rpenido]

Hi @kdmccormick! This was implemented (with some changes) on openedx/openedx-platform#37286 and now on openedx/openedx-platform#37567.

Please let us know if you think we need to make any adjustments.