Function encode_phc 

pub fn encode_phc(params: &Params, salt: &[u8], tag: &[u8]) -> String

Encode an Argon2id hash in the PHC string format: $argon2id$v=19$m=<m_cost>,t=<t_cost>,p=<p_cost>$<salt_b64>$<hash_b64>

Uses base64 encoding without padding (standard alphabet with +/ replaced by the PHC-standard base64 which is actually the standard base64 without padding).