Static PKCS_ECDSA_P521_SHA384 

pub static PKCS_ECDSA_P521_SHA384: SignatureAlgorithm

ECDSA signing using the P-521 curves and SHA-384 hashing as per RFC 5758

Note that this algorithm is not widely supported, and is not supported in TLS 1.3.

Only supported with the aws_lc_rs backend.