Add missing listOidcProviderConfigs method. (#406)

Each asynchronous method is supposed to have a synchronous counterpart. This was supposed to be included when I initially added the operation to list OIDC provider configs.

Author: micahstairs

src/main/java/com/google/firebase/auth/AbstractFirebaseAuth.java

@@ -1198,6 +1198,22 @@ protected OidcProviderConfig execute() throws FirebaseAuthException {
     };
   }
 
+  /**
+   * Gets a page of OIDC Auth provider configs starting from the specified {@code pageToken}. Page
+   * size will be limited to 100 provider configs.
+   *
+   * @param pageToken A non-empty page token string, or null to retrieve the first page of provider
+   *     configs.
+   * @return A {@link ListProviderConfigsPage} instance.
+   * @throws IllegalArgumentException If the specified page token is empty
+   * @throws FirebaseAuthException If an error occurs while retrieving provider config data.
+   */
+  public ListProviderConfigsPage<OidcProviderConfig> listOidcProviderConfigs(
+        @Nullable String pageToken) throws FirebaseAuthException {
+    int maxResults = FirebaseUserManager.MAX_LIST_PROVIDER_CONFIGS_RESULTS;
+    return listOidcProviderConfigsOp(pageToken, maxResults).call();
+  }
+
   /**
    * Gets a page of OIDC Auth provider configs starting from the specified {@code pageToken}.
    *
@@ -1208,7 +1224,7 @@ protected OidcProviderConfig execute() throws FirebaseAuthException {
    * @return A {@link ListProviderConfigsPage} instance.
    * @throws IllegalArgumentException If the specified page token is empty, or max results value is
    *     invalid.
-   * @throws FirebaseAuthException If an error occurs while retrieving user data.
+   * @throws FirebaseAuthException If an error occurs while retrieving provider config data.
    */
   public ListProviderConfigsPage<OidcProviderConfig> listOidcProviderConfigs(
         @Nullable String pageToken, int maxResults) throws FirebaseAuthException {
@@ -1228,9 +1244,8 @@ public ListProviderConfigsPage<OidcProviderConfig> listOidcProviderConfigs(
    */
   public ApiFuture<ListProviderConfigsPage<OidcProviderConfig>> listOidcProviderConfigsAsync(
       @Nullable String pageToken) {
-    return listOidcProviderConfigsAsync(
-        pageToken,
-        FirebaseUserManager.MAX_LIST_PROVIDER_CONFIGS_RESULTS);
+    int maxResults = FirebaseUserManager.MAX_LIST_PROVIDER_CONFIGS_RESULTS;
+    return listOidcProviderConfigsAsync(pageToken, maxResults);
   }
 
   /**