Adding an image url via Media Library should also populate image alt text field

My attempt at patching this.

Updated the patch because of a bug we've seen with certain schemas

3342759-4.patch

This patch is the same as 4 (it auto adds the image height and width when inserting an image via the Drupal module), but this is built from 9.1.x.

The check we had for 'image.src' was catching other fields we didn't expect. We've narrowed it down to only look for the .image.src field and added an additional fallback if the corresponding field isn't available in json editor.

Rerolled for 9.1

I've pushed up some work here to build on top of the patch from #6 and #7. My primary concerns with that implementation was a number of assumptions that are potentially site-specific:

• The selected media entity has a field named field_media_image
  • This is the default name for an image media type, so the assumption isn't terribly risky
• The target pattern has several additional fields at the same level for population:
  • alt
  • width
  • height
• These additional fields are not represented on the committed image pattern and would need to be added for testing and validation.

In the new commit I've added, the field name is addressed by looking it up from the media entity's field configuration. Regarding the assumed schema field names, I've built on the existing logic looking for the src attribute and allowed it to add the values for the additional fields and fail silently otherwise.

Since this only affects the image url solution, and not the media token solution that is now recommended, I'm not too concerned about adding additional testing and refactoring the example patterns to automate tests for this.

slucero → credited bladwin → .

I've now finished addressing most of the code review feedback an pushed up several improvements to the MR that should make it significantly more robust and user-friendly in the case of a failure.

slucero → credited msharma → .

This has been reviewed an tested internally. It is now approved for merging.

Merged for inclusion in the 1.2 release.