[WIP] Sarine API

[inha-kim]

Docs Checklist

Please ensure you have addressed documentation updates if needed as part of this PR:

• I have created a separate PR on the sequence docs repository for documentation updates: Link to docs PR
• No documentation update is needed for this change.

Remaining work:

• I was unable to test the endpoints with eth client calls since there was an ABI decoding issue. Andy was looking into this, so once that is wrapped up the endpoints can be tested with those properly. For now, the helper functions have the eth client calls commented out and will return a hardcoded mock data value
• The mock data values for ERC721 contract calls are faulty and so the functionality remains untested
• Mock data for Sarine marketplace api calls remain untested

I don't have any days remaining and am blocked by work from Sequence side so I'll leave the ticket here, but the remaining work should ideally be as simple as uncommenting implemented features, once blockers are resolved.

#307 should be merged before this