Performs an HTTP request from the extension's background service worker instead of the
calling context, then reconstructs a real Response from the serialized reply.
Serializable subset of RequestInit accepted by backgroundFetch. Only
structured-cloneable fields are supported; body must already be a string (callers
stringify JSON themselves).
Performs an HTTP request from the extension's background service worker instead of the calling context, then reconstructs a real Response from the serialized reply.