Token (& token type) machine name requirements

Thanks for this patch @gadaniels72, it worked for me!

I'll prepare a MR and fix this tomorrow. Thank you all!

Thanks, merged! :)

Automatically closed - issue fixed for 2 weeks with no activity.

Does this update take into consideration existing machine names using underscores?

After updating to 8.x-1.0-beta1, we cannot edit any of our existing tokens. I've provided a screenshot of what we now see:

Not being able to edit existing token content is really problematic. I think this update should be reverted. See https://www.drupal.org/project/token_custom/issues/3507564 🐛 Can't edit existing tokens after beta1 update Active

Indeed the commit shows a bug, underscores should be allowed, but are not. Let's fix that regression in:
🐛 Can't edit existing tokens after beta1 update Active