Summary:
https://github.com/facebook/flipper/pull/2080 enables storing protobuf definitions and displaying payloads in the network inspector plugin. However, describing those definitions in ProtobufJS format can be time consuming and error prone. This PR enables sending definitions from an entire Retrofit service with a single line.
## Changelog
* Adds a retrofit2-protobuf plugin
Pull Request resolved: https://github.com/facebook/flipper/pull/2084
Test Plan:
Used as a single line per service, ie:
`SendProtobufToFlipperFromRetrofit(baseUrl, PersonService::class.java)`
For more details see demo app in https://github.com/hbmartin/protobuf_java_to_protobufjs
Reviewed By: mweststrate
Differential Revision: D27507872
Pulled By: passy
fbshipit-source-id: 859d7636c9512de0abde0aa1dcb2e023851369cf
