[FEAT] Reimplement Claiming of External Offers in GraphQL API

[srhinos]

The Playwright implementation would claim external offers and write codes and their redemption instructions to a file.

This should achieve the same 1:1 implementation of fetching external offers, claiming them, then writing the Code and the redemption instructions to file in the same format as before (see code_to_file function in Playwright implementation for more info)