RDAP: Document RDAP guidance

Updates the RDAP code to reflect guidance and confirmation received from various mailing lists.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=129254894

javatests/google/registry/rdap/RdapJsonFormatterTest.java

@@ -295,6 +295,18 @@ public class RdapJsonFormatterTest {
         .isEqualTo(loadJson("rdapjson_techcontact.json"));
   }
 
+  @Test
+  public void testRolelessContact() throws Exception {
+    assertThat(
+            RdapJsonFormatter.makeRdapJsonForContact(
+                contactResourceTech,
+                false,
+                Optional.<DesignatedContact.Type>absent(),
+                LINK_BASE,
+                WHOIS_SERVER))
+        .isEqualTo(loadJson("rdapjson_rolelesscontact.json"));
+  }
+
   @Test
   public void testDomain_full() throws Exception {
     assertThat(