Allow admins to access registrar console without a RegistrarContact

This allows admins to access the registrar console without needing to be added
as a registrar contact. If they are a registrar contact, then that registrar
takes precedence.

Tested=In Alpha

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=164182623

java/google/registry/config/RegistryConfig.java

@@ -931,6 +931,16 @@ public final class RegistryConfig {
       return config.registryPolicy.checkApiServletClientId;
     }
 
+    /**
+     * Returns the clientId of the registrar that admins are automatically logged in as if they
+     * aren't otherwise associated with one.
+     */
+    @Provides
+    @Config("registryAdminClientId")
+    public static String provideRegistryAdminClientId(RegistryConfigSettings config) {
+      return config.registryPolicy.registryAdminClientId;
+    }
+
     @Singleton
     @Provides
     static RegistryConfigSettings provideRegistryConfigSettings() {

java/google/registry/config/RegistryConfigSettings.java

@@ -78,6 +78,7 @@ public class RegistryConfigSettings {
     public String tmchCrlUrl;
     public String tmchMarksDbUrl;
     public String checkApiServletClientId;
+    public String registryAdminClientId;
     public String reservedTermsExportDisclaimer;
     public String whoisDisclaimer;
   }

java/google/registry/config/files/default-config.yaml

@@ -71,6 +71,11 @@ registryPolicy:
   # domain checks.
   checkApiServletClientId: TheRegistrar
 
+  # The registry admin's registrar. Admins are granted permission to log in
+  # using this registrar automatically if they are not associated with any
+  # registrar
+  registryAdminClientId: TheRegistrar
+
   # Disclaimer at the top of the exported reserved terms list.
   reservedTermsExportDisclaimer: |
     This list contains reserved terms for the TLD. Other terms may be reserved

java/google/registry/config/files/nomulus-config-production-sample.yaml

@@ -29,6 +29,7 @@ registryPolicy:
   tmchCrlUrl: http://crl.icann.org/tmch.crl
   tmchMarksDbUrl: https://ry.marksdb.org
   checkApiServletClientId: placeholder
+  registryAdminClientId: placeholder
   whoisDisclaimer: |
     multi-line
     placeholder