Add RDAP support for deleted nameservers and filtering by registrar

This CL adds the functionality for nameserver searches. Future CLs will handle domains and entities.

Deleted items can only be seen by admins, and by registrars viewing their own deleted items.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=170106014

java/google/registry/rdap/RdapModule.java

@@ -61,4 +61,16 @@ public final class RdapModule {
   static Optional<String> provideHandle(HttpServletRequest req) {
     return RequestParameters.extractOptionalParameter(req, "handle");
   }
+
+  @Provides
+  @Parameter("registrar")
+  static Optional<String> provideRegistrar(HttpServletRequest req) {
+    return RequestParameters.extractOptionalParameter(req, "registrar");
+  }
+
+  @Provides
+  @Parameter("includeDeleted")
+  static Optional<Boolean> provideIncludeDeleted(HttpServletRequest req) {
+    return RequestParameters.extractOptionalBooleanParameter(req, "includeDeleted");
+  }
 }