Public API: defaultValue for Relation FieldType is not honored

Using the API, when creating a ContentType with a Relation FieldType attribute (FieldDefinition), the defaultValue property for the FieldDefinition will not be honored, regardless if the value assigned to it is a Content ID (int) or a ContentInfo.

Steps to Reproduce:To reproduce:

1. Using the API, create a ContentType with a Relation FieldDefinition
2. Set the FieldDefinition `defaultValue` property to an existing Content ID or ContentInfo
3. Verify through the interface that the attribute does not contain a default value.