Inject a singleton Gson instead of creating it many times (#3058)

Creation of Gson objects is nontrivial and it's thread-safe so we might
as well just use some singleton objects as much as possible rather than
recreating them.

core/src/test/java/google/registry/bsa/api/BsaCredentialTest.java

@@ -28,9 +28,11 @@ import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
 
+import com.google.gson.Gson;
 import google.registry.keyring.api.Keyring;
 import google.registry.request.UrlConnectionService;
 import google.registry.testing.FakeClock;
+import google.registry.tools.GsonUtils;
 import java.io.ByteArrayInputStream;
 import java.io.IOException;
 import java.io.OutputStream;
@@ -49,6 +51,7 @@ import org.mockito.junit.jupiter.MockitoExtension;
 class BsaCredentialTest {
 
   private static final Duration AUTH_TOKEN_EXPIRY = Duration.ofMinutes(30);
+  private static final Gson GSON = GsonUtils.provideGson();
 
   @Mock OutputStream connectionOutputStream;
   @Mock HttpsURLConnection connection;
@@ -60,7 +63,8 @@ class BsaCredentialTest {
   @BeforeEach
   void setup() throws Exception {
     credential =
-        new BsaCredential(connectionService, "https://authUrl", AUTH_TOKEN_EXPIRY, keyring, clock);
+        new BsaCredential(
+            connectionService, "https://authUrl", AUTH_TOKEN_EXPIRY, keyring, GSON, clock);
   }
 
   void setupHttp() throws Exception {

core/src/test/java/google/registry/testing/ConsoleApiParamsUtils.java

@@ -20,7 +20,7 @@ import static org.mockito.Mockito.when;
 import com.google.common.collect.ImmutableList;
 import google.registry.groups.GmailClient;
 import google.registry.model.console.User;
-import google.registry.request.RequestModule;
+import google.registry.request.Modules;
 import google.registry.request.auth.AuthResult;
 import google.registry.security.XsrfTokenManager;
 import google.registry.ui.server.SendEmailUtils;
@@ -50,6 +50,6 @@ public final class ConsoleApiParamsUtils {
         authResult,
         sendEmailUtils,
         xsrfTokenManager,
-        RequestModule.provideGson());
+        Modules.GsonModule.provideGson());
   }
 }

core/src/test/java/google/registry/tools/AuthModuleTest.java

@@ -55,6 +55,8 @@ class AuthModuleTest {
   private static final String ACCESS_TOKEN = "FakeAccessToken";
   private static final String REFRESH_TOKEN = "FakeReFreshToken";
 
+  private static final Gson GSON = GsonUtils.provideGson();
+
   @SuppressWarnings("WeakerAccess")
   @TempDir
   Path folder;
@@ -166,7 +168,7 @@ class AuthModuleTest {
   void test_provideLocalCredentialJson() {
     String credentialJson =
         AuthModule.provideLocalCredentialJson(
-            AuthModuleTest::getSecrets, this::getCredential, null);
+            AuthModuleTest::getSecrets, GSON, this::getCredential, null);
     Map<String, String> jsonMap =
         new Gson().fromJson(credentialJson, new TypeToken<Map<String, String>>() {}.getType());
     assertThat(jsonMap.get("type")).isEqualTo("authorized_user");
@@ -182,7 +184,10 @@ class AuthModuleTest {
     Files.writeString(credentialFile.toPath(), "{some_field: some_value}");
     String credentialJson =
         AuthModule.provideLocalCredentialJson(
-            AuthModuleTest::getSecrets, this::getCredential, credentialFile.getCanonicalPath());
+            AuthModuleTest::getSecrets,
+            GSON,
+            this::getCredential,
+            credentialFile.getCanonicalPath());
     assertThat(credentialJson).isEqualTo("{some_field: some_value}");
   }