Check a base URL against the library's rules (baseUrlProblem: no whitespace or
control characters, an absolute http(s) URL, no query or fragment) and return it
without trailing slashes. Throws PegelValidationError Invalid baseUrl: …: a
configuration mistake, not a PegelNetworkError. The RequestEngine constructor
calls it on the raw value, so a custom transport never sees a bad base URL; the
default transport still re-checks the scheme on every hop.
Check a base URL against the library's rules (baseUrlProblem: no whitespace or control characters, an absolute http(s) URL, no query or fragment) and return it without trailing slashes. Throws PegelValidationError
Invalid baseUrl: …: a configuration mistake, not a PegelNetworkError. The RequestEngine constructor calls it on the raw value, so a custom transport never sees a bad base URL; the default transport still re-checks the scheme on every hop.