in service settings tab create a field with the follwing values
ID- domainname
Name- Domain Name
Class-domain-name
Element type-domain name
Minterms-1
Maxterms-1
here customer can select add only one domain because minterms and maxterms entered as 1.
or else you can use only ID,Name,class=domain-name this also work fields like
Element type-domain name
Minterms-1
Maxterms-1
are not mandatory