MOIA-29747: Use GitHub Actions

[saeltz]

Migrates from CircleCI to Github Actions:

• ubuntu-latest container already includes latest sbt and Scala. No need to use our moia-CircleCI-image.
• Uses caching to make it fast.

For deployment:

• Remove folder .circleci. Push.
• Merge this.

[m-dobler]

I am completely new to Github actions, so I have some questions just for my learning:

1. I like the changes to the UI, are there any other advantages/reasons why we want to change to Github Actions?
2. And why are Github actions considered the preferred solution for open-source projects?
3. Why didn't you delete the circleCI workflow in this PR?

[saeltz]

1. Basically, it's cheaper for the company. Everything is inside GitHub. The actions actually make your CI code shorter.
2. We start with open-source projects because it's a little bit more complicated to use secrets within GitHub Actions. We obviously don't want to share them within the yml.
3. CircleCI is still on the master, so it will run anyways but fail. We have to delete it first and then merge this in a second step.

[JannikArndt]

Hm, https://github.com/moia-dev/scala-http-client/pull/52/checks?check_run_id=713158573 says

Cache SBT & ivy cache
Cache not found for input keys: Linux-sbt-ivy-cache-687320df953ec21e7e8b42a5e015bcfd9c615f6a11d7c002c2886cbe683d17f7-95ba01dd0aaf44d45145d38239552f4a1797d1116707d2a72fd356815ed4d725-eca9582a2998fd975f40c53cb1f63adb3eb3061e8ca453977b6c0bce7b08bf89.

and then

Post Cache SBT & ivy cache
[warning]reserveCache failed: Cache already exists. Scope: refs/heads/MOIA-29747-actions, Key: Linux-sbt-ivy-cache-687320df953ec21e7e8b42a5e015bcfd9c615f6a11d7c002c2886cbe683d17f7-95ba01dd0aaf44d45145d38239552f4a1797d1116707d2a72fd356815ed4d725-eca9582a2998fd975f40c53cb1f63adb3eb3061e8ca453977b6c0bce7b08bf89, Version: (null)

The keys are the same. What does the version mean? And how are we supposed (by GitHub) to find those warnings? 😄

[saeltz]

The keys are the same. What does the version mean? And how are we supposed (by GitHub) to find those warnings? 😄

You need to know that there exists a new version 2 of the cache action which supports multiple paths which I intended to use but still used v1. Now caching works.

Only thing that bothers me is that if the cache is outdated, all steps that run in parallel (compile, examples, formatting, scapegoat) download all the dependencies. Only way around is to make all of them depend on (need) compile step to finish.