fix: throw error with duplicate action key

[gioboa]

This commit change the behavior with actions with the same name.
Based on the issue description I changed warnings into errors.

Close #26

Checklist (if applicable):

• PR title is following https://www.conventionalcommits.org/en/v1.0.0/
• Tested (manually, unit tested, etc.)
• Docs updated (updated docs or a docs bug required)

[MichaelDoyle]

Hey @gioboa - just checking - it looks like this PR only changes the "log level" from warning to error, and does not actually raise any error. Based on the PR title, though, I think you intend to throw an error?

[gioboa]

Hey @gioboa - just checking - it looks like this PR only changes the "log level" from warning to error, and does not actually raise any error. Based on the PR title, though, I think you intend to throw an error?

Yep, you are right. I fixed the code to get the desired behavior.

[gioboa]

Thanks for your review @MichaelDoyle
I'm looking forward to getting your feedback about the change.