Add support for TLS 1.3 Diffie-Hellman-PSK combo key exchange mode
TLS 1.3 supports three key exchange modes:
- Diffie-Hellman (of both the finite field and elliptic curve varieties).
- A pre-shared symmetric key (PSK)
- A combination of a symmetric key and Diffie-Hellman
This issue is about adding the TLS 1.3 DDiffie-Hellman-PSK combo key exchange mode in GnuTLS