api: Canonical/consistent formats for responses

[cmwaters]

From an external team:

There’s not consistent/canonical formats for a lot of responses, especially merkle proofs and namespaced rows/blobs. We’ve been able to outsource to Lumina, but IIRC we used to have to declare 3 or 4 different share responses types that contained the same logical information laid out in different (incompatible) ways.