Use "async" as a revive field formatter fallback, if no invocation method was provided

Hi,

thanks for creating the issue and proposing a patch.

When the entity is rendered in a view mode that contains the field, it will result to a fatal error, as there is no invocation method

I can confirm this.

and also there is no way to select an invocation method.

This is actually not true, but maybe not that super obvious. In that case you need to specify the invocation method on the "Manage display" settings of your entity. Then there will not be a fatal error.

But I agree, that a global setting could make sense here and such a fatal error should not happen in any case. Then there wouldn't be any further configuration required on the per-block or per-entity base.

Attaching a patch, that tests the given scenario. It should fail and will be used to prove that the patch #2 is fixing the issue.

And a patch with proper test and patch #2 included. That should ideally pass successfully.

New test against the current dev, using the new test trait.

We agreed in a side-disussion, that it should be enough, just to make sure, that the fallback field formatter is the "Async" method, simply because we expect it to be the most used one. That will prevent the fatal error.

We should document this behavior and also fact, that the Invocation method can be changed on the "Manage display" field formatter level.

A global invocation method is nice, but we don't see much use-cases, where someone would choose for example "iframe" globally for the site.

Here's a patch for using the "async_javascript" method as a defaultsetting. If the test returns green, the fatal error should not happen anymore.

Merged into the dev-release. Thanks for the contribution!