url: add TryFrom<&[u8]> for Url and TryFrom tests

[acfoltzer]

Per discussion on Matrix.

I didn't realize when first asking that TryFrom<&str> is already implemented, but hasn't been released. So, I ended up just adding the impl for byte slices, an error variant for invalid UTF-8 inputs, and tests for the impls.

[acfoltzer]

I believe CI is failing because a credential is not available from my fork.

[SimonSapin]

I feel this should not be implemented. URL parsing is defined over Unicode input. &[u8] and &str are not interchangeable representations of "the same thing", Unicode and bytes are separate "domains" of data and the choice of strict UTF-8 decoding for converting between them should be explicit to users.

(Unfortunately the Matrix link doesn’t seem to work from here.)

[acfoltzer]

@SimonSapin I definitely agree with you on these being separate domains of data, but I believe that's reflected by the use of TryFrom (rather than From) and the addition of the InvalidUtf8 error variant.

There wasn't much discussion on Matrix really:

[djc]

FWIW, like @SimonSapin I think this is a bad fit.

[acfoltzer]

No worries, again it's just a convenience and not a dealbreaker for our adoption.