using-openapi-generator-swift5

[etoledom]

This is an alternative to https://github.com/Automattic/Gravatar-SDK-iOS/pull/248

On this PR we use https://openapi-generator.tech/docs/generators/swift5/ instead of https://github.com/apple/swift-openapi-generator .

Benefits over Apple's generator:

• We can choose to generate and use a model without external dependencies.
• We can use our own Service infrastructure to make the request, without the need of the generated client.
• All model seem to be generated properly, and with camelCased fields.
  • The Apple's generator seems to have issues with a couple of types like here.

Drawbacks over Apple's generator:

• This generator is a Java cli.
• To avoid all Java dependencies, I opted for a Docker based option.
  • Docker needs to be installed and running to generate the code.
• The generated structures used by profile (like ProfileContactInfo) are not nested to the Profile struct. This is not terrible but it would be a nice-to-have.
• Generating the code with make install-and-generate (when openapi-generator have not been yet cloned) is really slow.

On this example, I opted for having Profile public, I'm not very happy with this, but the extra boilerplate of wrapping it in a different struct seems unnecessary now, keeping in mind that we can have control (or at least a vote) on yaml spec changes (up to debate).

Testing Steps

[etoledom]

@pinarol - I believe this is ready for review 👍