Migrate to GitHub actions

[BillyAutrey]

• Removes Travis config and the Travis SBT plugin, since builds with Travis are disabled now.
• Uses Play Framework's standard playframework/.github/ workflows to run tests.
• Adds in format checking with scalafmt.

Notes:

• Travis is disabled, so it won't run.
• Publish is untested. I'm just assuming here that it'll work with the inherited .github keys/secrets, but it needs to be tested.
• I had to back down to a less recent Scala 2.13 version (that matched what was in travis.yml, because tests failed with more recent versions.

[mkurz]

A couple of things. Please also remove the travis status check from the repo settings and add the "Finish / Ready To Merge" one instead.

Actually this project does not have sbt-ci-release set up already, so this needs to be done as well... (It was/is my plan to set that up for every repo as soon as Sergey reviewed and merged GHA pull request in the .github repo, since that is the final piece for me that is missing to go through each repo and correctly set up GHA everywhere, including sb-ci-release.)

[mkurz]

Not sure if this set publish/skip... should actually be configured in build.sbt itself. Also probably we should make sure we only call publish for the play-grpc project? Or maybe configure the build correctly so that only publish will do... I have to check tomorrow as I am to tired now...

[BillyAutrey]

Note, play-grpc seems to be the aggregate rule. There are several projects that look like they are published, if you run publish from the aggregate:

• "play-grpc-runtime"
• "play-grpc-testkit"
• "play-grpc-specs2"
• "play-grpc-scalatest"
• "lagom-javadsl-grpc-testkit"
• "lagom-scaladsl-grpc-testkit"

Many of them seem viable to eventually publish. For instance, having separate modules for test suites feels like a reasonable thing to do. But I guess this project is still somewhat in flight.

I added the build.play.grpc.NoPublish to play-grpc-generators, since it's skipped in the travis rule. It also feels like it could be useful to publish, but better to keep things as-is for now I guess.

[BillyAutrey]

A couple of things. Please also remove the travis status check from the repo settings and add the "Finish / Ready To Merge" one instead.

Done.

Actually this project does not have sbt-ci-release set up already, so this needs to be done as well... (It was/is my plan to set that up for every repo as soon as Sergey reviewed and merged GHA pull request in the .github repo, since that is the final piece for me that is missing to go through each repo and correctly set up GHA everywhere, including sb-ci-release.)

If we're waiting on some common work to be finished, I can cut another PR once that work is complete. Not having checks prevents us from doing scala-steward merges though, which I think are important.

[BillyAutrey]

These tests are quite flakey. Might need to take a pass at stabilizing them soon.