Returns servers[0].url only when it is usable as a BoundFetch base URL: absolute http/https, no {variables}, and not a relative path. Otherwise returns undefined (callers should use explicit baseUrl / defaultBaseUrl).
servers[0].url
http
https
{variables}
undefined
baseUrl
defaultBaseUrl
Returns
servers[0].urlonly when it is usable as a BoundFetch base URL: absolutehttp/https, no{variables}, and not a relative path. Otherwise returnsundefined(callers should use explicitbaseUrl/defaultBaseUrl).