LegacyUserAgent.get(url: string,headers?: Record<string, string>): Promise<{ result: LegacyHttpResult; }>
headers, when given, are merged on top of this instance's own default headers (set via
transactor/on) for this one request only — mirrors real
Mojo::UserAgent's own ->get($url => {'Header-Name' => 'value'}) calling convention.
Promise<{ result: LegacyHttpResult; }>