By default, you have very few options for field validation in Drupal. You can make a field required, set its length if you have a text field, or set the allowed number of values -- but that's just about it. Fortunately, we have a very powerful mechanism for adding field validation.
Entity Reference and Entity Reference Revisions fields are very similar, but the latter offers more flexibility when it comes to reverting to a previous revision in the case when you have a nested entity. Let's see the easiest way to migrate an existing Entity Reference field to an Entity Reference Revisions field.
Pseudo fields are a special type of field that you can add to any content entity type. Let's see how to add this kind of field to the form and entity displays.
A recent tweet by CHX got me thinking. Drupal 8 was released almost 5 years ago, and some things are still a mystery for a lot of developers, including me. Let's explore the various ways of updating field values in Drupal 8 and 9.