Update base path configuration for OpenAPI 3

[romanblanco]

Problem

API Host and base URL definition has changed from OAS2 to OAS3.

schemes, host and basePath definitions are being replaced by Server Object

This is causing issue #318.

Closes #397
Closes #318

Solution

I'm building on top of @developingchris's approach from #397.
The solution is to parse the URL from the Server Object.

This concerns this parts of the Open API Specification:

• OAS2.0: API Server and Base URL
• OAS3.0: API Server and Base URL

The changes I made are compatible with:

• OAS2
• OAS3
• OAS3.1

Related Issues

• OAS v3 tests fail without basePath, but basePath generates invalid Swagger #318

Checklist

• Added tests
• Changelog updated
• Added documentation to README.md

Steps to Test or Reproduce

see #318

[romanblanco]

Hi @jtannas, could you look at the changes to see if it makes sense to you?

[jtannas]

Thanks for the contribution! 🙂
I really appreciate the help while I'm getting this all figured out.

Just a few notes on places I found difficult to follow and it should be good to go!

[romanblanco]

@jtannas Thanks for keeping the Gem alive!

I've applied the suggested changes (diff). Let me know if you see more things to improve 🙂