feat: set the shell for workflow command steps

[anryko]

what

Added an option to define the shell for the custom workflow steps with the command filed, like run, env, and multienv.

why

• This change simplifies writing more elaborate shell logic.
• The same functionality is achievable by running command: bash -c "my inline shell script", but dealing with double quote escaping within the shell script is quite cumbersome.
• The default busybox shell is limited and having "native" access to bash will improve user experience.

tests

• I run the unit tests.
• I verified manually tested this functionality on a local setup.

references

• Closes: Allow Specifying Custom Script Runner #1417

[X-Guardian]

Hi @anryko, thanks for this. Any chance you can follow the same pattern as the pre/post workflow hooks to have the ability to specify the shell and shellargs. See https://www.runatlantis.io/docs/pre-workflow-hooks.html#reference.

I also see no reason to limit the shell to bash and sh.

[anryko]

@X-Guardian sure, I'll do that. I would suggest to make shellArgs to be a list. This would make sense because it's a list of arguments and will be consistent with extra_args property (like plan.extra_args []string).

[anryko]

@X-Guardian I added support for shellArgs and removed the limit for the shell option as it was suggested.