Feature/provide PartialEq and Eq derives for the HttpApiProblem struct

[awaltert]

Hi @chridou,

we want to use this crate for our projects and stumbled over a tiny limitation. We need the ability to compare HttpApiProblem structs. The current implementation provides a PartialEq and Eq derive for the testing profile. I suggest providing those two derives in general as this would also make it usable for other use cases.

Changes:

• Move the derives from the test profile to the general availability
• Bump the crate version
• Ensure that the test cases still run successfully
• Document the change in the Changelog.md

Looking forward!