Make target and targets attributes optional for Stream actions

[marcoroth]

With the introduction of Custom Stream Actions we can now create Stream Actions that not necessarily require a target attribute to be present.

In order to keep the behaviour we need to raise an ArgumentError if no target was passed to a default stream action helper.

This Pull Request adds a constant with the default actions which require a target or targets attribute to be present. For any other action it will return a regular <turbo-stream> tag without the target attribute.

Edit: This Pull Request removes the check and thus makes the target and targets attributes optional for stream actions.

Related: #373 and #374

[dhh]

Don't actually think we need this degree of error checking. We're just generating an HTML tag here. Fine to simply allow it not to have a target, and thus be invalid, if the action requires a target.

[marcoroth]

I just added the check so that we can remain the behavior between versions. Because applications could technically rely on this error to be thrown, but I would be fine to remove the check entirely.

[dhh]

I'd say just remove the check. Don't see how an app will rely on this. It's a failure state.