Feature/formats

[ehmicky]

This PR aims at converting the formats defined only by OpenAPI but not in JSON schema v4, into something that is valid JSON schema v4.

All JSON schema v4 formats are left as is. Custom formats are also left as is. However the following OpenAPI-only formats are converted by adding extra keywords:

• int32, int64, float, double: add related minimum and maximum keywords
• byte: add pattern keyword to match base64. We are using standard base64, not base64url, as this is what is intended
• password and binary: left as is since they are just semantic/UI hints

I respected the following principles of JSON schema v4:

• any format value is valid (i.e. custom formats are possible)
• keywords for a specific type (including a specific format) might appear even if the type is different

I added unit tests.

I also removed the format keyword from non-format related unit tests, as this makes tests inter-dependent. Indeed when working on this feature, some unit tests were failing even though they were related to another feature.

[mikunn]

This is good stuff, thanks!

We will probably need to make the base64 pattern a bit more strict before the next release or alternatively provide an option for a custom pattern.

Also, conversion related functions start to appear all over the place, so it's probably a good time to start modularising things a bit.

I will take a look on both of these.