Selectively replace 'large' image style in full node view mode with 'medium_large' supplied by debut_media

Problem/Motivation

Currently we're using the 'large' image style provided by the core image module to display the content_image field in full node pages. This creates display issues--the image typically is too large to float text around but doesn't fill the full width of the node display region, leading to awkward layout.

Since the content_image field appears in numerous debut features, we can't simply add a new image style to debut_article without creating a dependency on debut_article for other features using the same image style. Debut media provides a suitable image style, medium_large, but adding that to the exported fields would add a dependency on debut_media.

Proposed resolution

Using hook_field_default_fields_alter(), conditionally switch in the medium_large image style if debut_media is present.

This change should also include CSS to float the image.

Remaining tasks

Because fields are not true exportables, the resulting approach may be fragile and prone to breakage if, e.g., debut_media is not enabled prior to the article implementing the hook_alter, i.e., in this case, debut_article.

User interface changes

Images in full node view modes will be smaller and floated.

API changes

Requires introduction of debut_article_feature_is_regeneration() method to skip altering in the case that the feature is being regenerated.