[JAVA] Support for Retrofit2 client generation with Play! Async WS http-client

[lukoyanov]

Description

Seems no support for retrofit2 client that use Play's WS as a http-client. I could contribute a generator for play 2.4.

[wing328]

@lukoyanov thanks! Let us know if you need help or any starting point to begin the contribution.

[wing328]

FYI. Currently, Java API client already supports Retrofit2 (in additional to jersey1.x, jersey2.x, feign, etc). You may want to add the support by adding another option (e.g. usePlayWS) similar to parcelableModel.

For a full list of Java API options, please run java -jar modules/swagger-codegen-cli/target/swagger-codegen-cli.jar config-help -l java

[lukoyanov]

I've opened a PR core implementation + api key auth. #4263

[lukoyanov]

Created new PR, with proper history #4270

[wing328]

@lukoyanov thanks. I've left you some comments. Please let me know if you need help adding the Petstore samples with the enhancement you provided.

[lukoyanov]

@wing328 PR updated.

[wing328]

Closed via #4270. Thanks for the PR from @lukoyanov

[wing328]

@lukoyanov when you've time, I wonder i you can look at the issue when upgraing retrofit2 to the latest version 2.2.0 as found in #5235

[lukoyanov]

@wing328 I'll take a look in a few days.