Check a base URL against the library's rules (baseUrlProblem: an absolute
http(s) URL, no query or fragment) and return it without trailing slashes.
Throws ReiseValidationError Invalid baseUrl: …: a configuration mistake, not
a ReiseNetworkError. 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: an absolute http(s) URL, no query or fragment) and return it without trailing slashes. Throws ReiseValidationError
Invalid baseUrl: …: a configuration mistake, not a ReiseNetworkError. 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.