Function served_identity 

pub fn served_identity(
    terms: &ServedTerms,
    reported: Option<&str>,
) -> Result<ServedIdentity, IdentityMismatch>

The served identity to record, from the negotiated terms and what the remote side reported for this exchange.

• pinned: the pinned identity is recorded; a reported identity that differs is an IdentityMismatch.
• reported: a reported identity is recorded as reported; none is unknown.
• unknown: always unknown. A name the remote side offers anyway is not a served identity under these terms; the caller keeps it among the provider extras. Nothing is promoted, and the requested model is never copied into the served field.