ReadonlyactionReadonlyaddressID of the address to be extended.
Optional ReadonlyfieldsObject containing the Custom Fields fields for the address.
Required if at least one Custom Field is defined as required in the `fieldDefinitions` of the referenced [Type](ctp:api:type:Type).
Optional ReadonlytypeDefines the Type that extends the address with Custom Fields.
If absent, any existing Type and Custom Fields are removed from the address.
Adding or updating a Custom Type on an Address of a Business Unit generates the BusinessUnitAddressCustomTypeSet Message, and removing one generates the BusinessUnitAddressCustomTypeRemoved Message.