Uncomment Bazel code and set proper flags in order to enable and build HTTP3-QUICC features in the proxy. OpenSSL 3.5 should be used.

It will be necessary to accommodate & unify the two different approaches to QUIC in the Envoy code when passing from BoringSSL to OpenSSL.

In fact, BoringSSL takes a minimal approach, providing just the necessary callback/extension points to enable potential QUIC implementations full control over the protocol stack, allowing for the most efficient implementations.

In contrast to this, OpenSSL takes a much more comprehensive approach of implementing the full QUIC protocol itself, as transparently as possible under the existing OpenSSL API.