Extract login details improvements

[oguzkocer]

This PR dissects #46 and implements the Rust parts that still makes sense to include.

• Improves ParsedUrl to be a proper wrapper around url::Url. The point of this type is to be able to expose it through FFI and this setup should allow us to do that. It adds all variants of url::ParseError to ParseUrlError and a Generic error because url::ParseError is non-exhaustive. It adds some unit tests to test various error types - some of which is lifted from Add Login and URL Tests #46.
• Brings in OAuthResponseUrlError from Add Login and URL Tests #46, updating the extract_login_details_from_url implementation to return a Result. Also brings in the unit tests related to this from Add Login and URL Tests #46.

[jkmassel]

This was super quick and easy to integrate with Swift, and the tests look solid.

Approving for now, we'll add more test cases as users do weird things to it 😂