#[mls_span]Expand description
Instrument a high-level MLS operation as operation = "mls.<fn_name>" in
libxmtp’s canonical, OTEL-safe span form (err, skip_all). Use
#[mls_span(redact_error)] to log a fixed error field and return the original
error unchanged. Surfaces as xmtp.mls.* Collector metrics. See [span] for the shared rationale.