Add configurable and validatable schemes.

[glenncoppens]

Provided is a first approach of configurable but still "validatable" schemes with defaults still in place. As there were a number of issues mentioning this as a "necessary" feature (see: #25, #64 ).

Remarks:

• I tried to create a basic but open Validator contract and base, definitely open to feedback and improvements.
• By using a fluent code style (eg: fromString) I scratched my head a bit on how to properly pass in the scheme configuration at the right time. Why? In the fromString method the scheme was (and still is) immediately sanitized and validated, which doesn't leave much room to configure the SchemeValidator. So I've added an optional allowedSchemes parameter.
  • Also I've extracted the "making" of the Url object to comply with "single responsibility" as much as possible
• I do think that the scheme should be sanitized better using a regex according to https://datatracker.ietf.org/doc/html/rfc3986#section-3.1 (which is defined in the UriInterface)

[freekmurze]

Some of the tests are failing. Could you take a look? Feel free to up required versions.

[glenncoppens]

@freekmurze

Ah, now I see, http-message 1.0 is used in the matrix during 'prefer-lowest' (unfamiliar with the setup).

I'll remove the string typehint again from withScheme(string $scheme) as for now, to still have BC for older http-message versions? Might be better to update the typehints in another PR and then bump the required http-message to ^2.0.

Comin' up!

[glenncoppens]

@freekmurze Would you be able to rerun the tests?

[freekmurze]

Thanks! Could you also update the readme?

[glenncoppens]

Done!