Move the real submit buttons to inside the dialogs

[mgax]

• Change the dialogs to open inside the page editor form (fixes Consider rendering the dialogs inside the page edit form #59).
• Remove the hidden buttons and input fields; the user-visible controls inside the dialogs are now part of the form so we don't need to copy data and forward submit events.
• Because the dialogs live at the end of the <form> element, the newsletter buttons are no longer triggered when pressing <enter> in a field - fixes Submitting the page with <enter> activates the wrong button #58.
• Fixes Wagtail 6.2 – cancel spinner if the "save revision" action is cancelled #54.
• Fixes Buttons in the Campaign panel wrap inconsistently #57 (includes the changes in Better wrapping of campaign buttons #62).

[laymonage]

Happy with the overall changes here! The subtitle dialog can be simplified by passing the message string to the {% dialog %} tag directly.

Glad to see that the dialog-root-selector helps with reducing the Stimulus targets.

[mgax]

@laymonage thank you for the naming and phrasing suggestions. My brain was fried after too much messing with events, CSS, templates and whatnot 😅

[laymonage]

Happy with the changes here! Would be nice to completely prevent the "send test email" submission if the email field is left empty, but I couldn't find a way to trigger the browser's "required" popup from my brief research. One small typo but I think you can fix that as you merge.

[mgax]

Would be nice to completely prevent the "send test email" submission if the email field is left empty, but I couldn't find a way to trigger the browser's "required" popup from my brief research.

That used to work, when the dialog had its own form, that only contained the email input. I'm not sure what's going on with Wagtail's page edit form.

[laymonage]

That used to work, when the dialog had its own form, that only contained the email input. I'm not sure what's going on with Wagtail's page edit form.

Yeah it's because Wagtail's editor form has the novalidate attribute (reasons described in wagtail/wagtail#2942), so you'd have to temporarily remove the attribute while the test email dialog is shown (and to add it back again afterwards). A bit of trouble than it's worth for now, but may be something to look into in the future.