Function purge_cache 

pub async fn purge_cache(
    state: &SharedState,
    a: PurgeCacheArgs,
) -> Result<Value, ToolError>

Purges every backend holding entries for id, or – with dry_run – just lists them. 404 (not_found) when no compiled policy has a pair with that id, exactly like the Admin API’s DELETE. On a backend failure, reports what was purged before it as a cache_purge_failed error.