Channel binding interop across QUIC stacks (§6.1)

[arkstack-dev]

§6.1 binds SCRAM-SHA-256-PLUS channel binding material to the end-entity certificate from the QUIC TLS 1.3 handshake.

For implementers: does your QUIC library of choice (quinn, msquic, quiche, ngtcp2, lsquic, picoquic, s2n-quic, Java's incoming QUIC support, anything else) expose the negotiated end-entity certificate to application code in a way that matches the API a SCRAM client expects?

If not — where's the gap, and is it fixable at the library level or does the spec need to accommodate it?