feat(*): Add test_command input and exclude release tagged tests for pull request

[julienloizelet]

The Issue

Fixes #30

How This PR Solves The Issue

• By default, the test command launched on pull request workflow will be bats tests --filter-tags !release

With this, if the add-on test is tagged with the "release" tag, it won't be executed on pull request workflow:

# bats test_tags=release
@test "install from release" {
...
...
}

• On other workflow ("schedule", "push", etc.), the test command will be, by default, as before : bats tests

• If an add-on maintainer needs to pass a customized test command, there is a new available string input test_command.
  When the test_command input is not empty, it will be used to run the test.

Manual Testing Instructions

To test the final behavior, you can use my forked action and points to the last commit:

steps:
      - uses: julienloizelet/ddev-add-on-test@b6b8c765ddba5fa511c2f9284e818d7fa3230f27
      with: 
          ...

How to test

1. Backward compatibility : Create a pull request on your add-on: If you have no "release" tagged test, all test should be run as before

2. Exclude "release" test: Tag a test with the "release" tag. This test should not be executed on PR workflow.

3. Customized test_command: Use the test_command input to see if your customized test command is launched.

4. backward compatibility (hard to test: you can modify the tests.yml workflow to be triggered during a push on a testing branch that contains the new action). Ensure that the launched command, for a non pull request workflow, is as before (bats tests) and that all tests are runned.

[stasadev]

Thank you @julienloizelet, I tested it with julienloizelet/ddev-add-on-test@b6b8c765ddba5fa511c2f9284e818d7fa3230f27 on https://github.com/stasadev/ddev-redis and it works perfectly.

I only have a small suggestion.

[rfay]

Awesome initiative, thanks!

[stasadev]

I checked again, everything works as it should, thank you!

[rfay]

What a great improvement, thanks!