Question: Why not separate Authentication-only spec?

[joemphilips]

It seems that specification.md can be separated into two parts

1. Authentication with x-identity,x-signature-type and x-signature and safe pubkey distribution

• This seems to be the updated version of bitpay's bitauth

2. Spec for payment request/response.

But since the simple transaction style payment is not the only way wallets works (e.g. commitment to Assurance Contracts, LN), It seems to me that separating Authentication-specific part and payment-specific part makes more sense. Am I missing something here?