eBay OAuth & Draft Listing Setup

I have a live (production) eBay seller account and I need a developer who can set-up my credentials all the way through the OAuth 2.0 Authorization Code Grant Flow in Postman, prove that the process works by returning a valid access token, and then use that token to create brand-new draft listings through the Sell and Inventory APIs.

Scope of work
• Configure my production key set inside a Postman environment, adding the necessary variables, pre-request scripts, and collections.
• Complete the full authorization dance—getting the user consent URL, exchanging the authorization code for the access and refresh tokens, and refreshing when required—without hitting 400 Bad Request or unauthorized_client errors.
• Provide a clear, repeatable Postman collection that I can re-run on demand.
• Build a sample request that creates a fresh draft listing which includes:
– Inventory items
– Offer details
– Shipping and return policies
• Return the full JSON responses so I can verify the listing in my seller hub.

Acceptance criteria
1. A working Postman environment/collection delivered in JSON format.
2. Access and refresh tokens obtained with no auth errors.
3. Draft listing visible in my production account containing the three data groups above.
4. Brief read-me (markdown or txt) explaining variable placement, common pitfalls, and how to refresh the token.

If you are comfortable troubleshooting OAuth flows, parsing eBay’s sometimes-cryptic error messages, and formatting Sell API payloads, I’d love to get this done quickly.