draft-ietf-oauth-transaction-tokens-04: Merge pull request #150 from gffletch/rename-azd-119

Updates to the draft include:

• cleaning up text around the transaction context claim
• updates to transaction token service responsibility
• IANA text cleanup
• clarifications for the subject_token_type
• updated guidance regarding mutual authentication
• updates to the Txn-Token response
• updated security considerations and privacy considerations

Includes the following merged PRs:
#116, #122, #123, #125, #126, #136, #138, #139, #140, #141, #142, #143, #144, #146, #147, #148, #150

draft-ietf-oauth-transaction-tokens-01

Update to the current transaction token draft

• better alignment with RFC 8693 Token Exchange
• updates to the way replacement transaction token work
• simplified subject claim to the standard sub claim
• started addressing how transaction tokens can be communicated to downstream workloads