v0.2.4

Added

• [breaking] implement SIP over TLS: Transport::Tls (RFC 3261 §26.2),
  a new tls cargo feature, certificate verification against the account's
  SIP domain (RFC 5922 §7.3) with optional SHA-256 pinning via TlsPolicy,
  and a typed CertFailure / UntrustedCertificate error surface
  (tls_error).

  This ships in the 0.2.x line by deliberate maintainer decision, so it is
  not a major-version bump — but it is not additive either. It carries three
  source-breaking changes, and cargo treats 0.2.x -> 0.2.y as compatible,
  so anything depending on "0.2" picks these up on a routine
  cargo update:

  • Transport gained a new variant, Transport::Tls. An exhaustive
    match on Transport in consumer code stops compiling — add an arm
    for Tls.
  • Transport is now #[non_exhaustive], so that match also needs a
    wildcard arm. This is deliberately bundled into the same release as
    the variant above: it is the last time adding a transport breaks a
    consumer. Every future variant is additive.
  • SipAccount gained a new field, tls_policy: TlsPolicy. Constructing
    the struct with a literal stops compiling — add
    tls_policy: TlsPolicy::default() (or your chosen policy).
    Deserialized configs are unaffected: the field is #[serde(default)],
    so no stored config file needs to change.