const github.com/refraction-networking/utls/dicttls.DHKEM_P521_HKDF_SHA512

one use

	github.com/refraction-networking/utls/dicttls (current package)
		hpke_kem_identifiers.go#L9: 	DHKEM_P521_HKDF_SHA512      uint16 = 0x0012 // RFC 5869