In the Structure
of your Properties
content type you can define the APN
field as an Object and you will get the option to use a complex object creator and visualizer for this field in the create/detail view of an entity.
Please note that doing so will have an UI-only effect, in the database you will be able to store any supported type and value to this field. Put simply, you only need to send the value of the field in the payload to the server and it will be written to the database, independent of the type you declared in the Structure
. You can read more about this here
For some fields like GeoPoint you still need to define them in the structure though. Same for setting a field value constraint as unique.
I hope this answers your question.