policy TLS_FORWARDING: rename pin to pin_sha256
The pin parameter contains SHA-256 encoded using Base64, but this is not the only option. Explicit name allows us to add alternative formats later on, and is consistent with GnuTLS naming.
The pin parameter contains SHA-256 encoded using Base64, but this is not the only option. Explicit name allows us to add alternative formats later on, and is consistent with GnuTLS naming.