Returns null when value is a usable trusted-proxy entry, otherwise the
reason it is not.
Mirrors the checkCanonicalIssuer / describeIssuerRejection pair in
../issuer/canonical.mjs: the check is reusable from a Zod superRefine
(which needs the reason to build a per-index issue) and from a plain
throw site (which needs the sentence).
Returns
nullwhenvalueis a usable trusted-proxy entry, otherwise the reason it is not.Mirrors the
checkCanonicalIssuer/describeIssuerRejectionpair in../issuer/canonical.mjs: the check is reusable from a ZodsuperRefine(which needs the reason to build a per-index issue) and from a plainthrowsite (which needs the sentence).