Make modal popup configurable

I agree with @dwkitchen: it would be great if we could configure when dialog is enabled and also if it should work automatically or not. With nested IEF I would suggest to disabled the automatic behaviour after the 1st IEF by default and maybe even not available from 2nd level nested IEF and deeper IEFs.

Automatic behaviour makes nested IEF almost unusable or at least counterintuitive, because the last nested child is the first one to be presented to the user automatically and also doesn't have a cancel option. So for example, a referenced product with multiple variations shows first the dialog to add a variation and only after adding one, the parent product form is shown. After adding one variation you can add another one by clicking the "Add new variation" button, which opens the form on a dialog, as expected.

IMO, the automatic option works only for first level IEF, but the popup dialog can be useful on child IEFs. I would add a radio button on the IEF widget (image attached) to disable the popup when it is not wanted and disable the automatic behaviour after the first level of nested IEF.

The only other module I see to get a similar functionality is entity browser but it adds extra complexity when only a popup is needed for IEFs. Thanks for your work on the module @dataweb and I hope the automatic functionality can be disabled so this module becomes useful for many more use cases.

@Drupalengue I added a MR with a possible approach. It gives the opportunity to activate or not the popup features for each ief widget.

Works like a charm @GuillaumePacilly. Good job!

I highly suggest to work with merge requests and the correct merge commit messages. Makes it way easier to track back commits to an issue.