Create and manage Discogs Marketplace listings via the authenticated Discogs API

Steps

1. Authenticate as the selling user (OAuth 1.0a user flow, or a personal access token for your own account) since marketplace listing creation always writes to the authenticated user's inventory
2. Send an authenticated request to create a new listing, including the release ID, a valid `condition` (one of the Discogs grading scale values: Mint, Near Mint, Very Good Plus, Very Good, Good Plus, Good, Fair, Poor), price, and comments
3. Optionally set `sleeve_condition` (which additionally allows Generic, Not Graded, or No Cover, unlike media condition), `allow_offers`, and shipping-relevant fields like weight and format quantity
4. Set `status` to `For Sale` to publish immediately or `Draft` to hold it back from public display until you finish setting it up
5. Read the newly created listing's ID from the response body and use it for follow-up updates (price changes, marking as sold) or deletions
6. Fetch the authenticated user's own inventory endpoint to verify the listing appears, noting that only `For Sale` status items are visible to non-owners