Sites can enable a JSON:API exposing Drupal entities to external clients. A setting allows data to be written in addition to the read-only default state.
Additional field properties can be set from a relationship object's optional meta object. This was due to a limitation in the special handling Drupal core performed around entity reference fields. In many cases, this may no longer be necessary; see this related change record.
Field properties which are specified in the meta object are now only added to the field value if the following are true.
- The property name is defined by the field.
- The property is not marked read-only or internal.
Sites that use a custom fields that depend on passing data to value arrays that do not correspond to properties are affected. These sites should update the fields to define these properties as needed.