PSBT field names

[tcharding]

Two questions relating to PSBT field names, please:

1. Why do we not use the matching identifiers for all fields as used it BIP-174? For example, some are the same PSBT_IN_TAP_INTERNAL_KEY => tap_internal_key but some are different PSBT_IN_TAP_BIP32_DERIVATION => tap_key_origins?

2. Why are some fields missing? For example, PSBT_IN_REQUIRED_TIME_LOCKTIME?

[DanGould]

1. naming is hard. i think consistency is a good idea

2. I think the missing fields are new to BIP370 psbt v2 and just haven't been added yet. the BIP174 spec was updated to include the new v2 fields

[apoelstra]

I think both these points are correct.

[sanket1729]

@tcharding, I copied the names from BIP371 in the bitcoin core pull requests. bitcoin/bitcoin#22558. I don't oppose renaming the fields to match the spec.