Two review findings on the fetch wrapper:
Reading the body with `response.text()` meant every successful JSON
response was rebuilt while overrides were configured, even when it was
not a metadata document. That dropped native properties a synthesized
`Response` cannot carry (`url`, `redirected`, `type`) from responses the
wrapper has no business altering, and threw outright on a body-less
204/205, whose status Fetch forbids a body on — so an unrelated transport
response could fail. It now parses a clone and returns the caller's own
response unless a document is actually patched.
`new URL` also accepts embedded credentials while Fetch rejects a request
URL carrying them, so `https://user:pass@host/token` passed both the form
and the runtime and then failed deep in the OAuth exchange.
`oauthEndpointUrlError` now rejects a username or password.
Signed-off-by: cliffhall <cliff@futurescale.com>