Function add_breadcrumb 

pub fn add_breadcrumb(
    message: &str,
    category: &str,
    level: &str,
    data: HashMap<String, Value>,
)

Records one entry into the current thread’s breadcrumb trail: a query, an outbound call, or anything worth remembering right up to the moment something actually goes wrong. category defaults to "custom" and level to "info" when passed an empty string. A no-op, not an error, when Configuration.track_breadcrumbs is false.

This crate has no web framework integration of its own (unlike sdks/go’s net/http/Gin middleware), so there’s no automatic breadcrumb source and no middleware to start a fresh trail per request on its own: call clear_breadcrumbs yourself at the start of each request, the same place you’d already be calling set_user from, or entries from an earlier request handled on a reused thread will bleed into this one’s own report.