Define parameters and terminology in appropriate sections

[dwaite]

From @OR13, https://mailarchive.ietf.org/arch/msg/jose/GkL3I9hEoKjaIDCgno_rYqQsSP0/ :

Assume the reader has some awareness of JOSE, and introduce terms like issuer_header and presentation_header so that they defined in their sections, for example:

https://datatracker.ietf.org/doc/html/draft-ietf-jose-json-proof-algorithms-00#name-presentation-protected-header-2

does not include "presentation_header" header.

[selfissued]

Typographically, we should use names like "Issuer Header" rather than issuer_header for things that are not parameter or field names.

[dwaite]

While this particular example seems solved, we have two general issues:

1. algorithmic values and JSON parameters may have the same choice in snake vs camel vs upper case - we may wish to have two styles here for clarity
2. we have definitions and processing steps in single use algorithm that should be raised to be generalized.