Currently we only support adding an endpoint suffix for azure repositories. This is not enough when a custom Azure DNS  zone is used since the URI that's created using an endpoint suffix is incorrect.
```java
primaryUri = new URI(protocol + "://" + accountName + "." + service + "." + endpointSuffix);
``` 

We should add the ability to provide a custom endpoint to cover this situations.
modules/repository-azure/src/test/java/org/elasticsearch/repositories/azure/AzureStorageServiceTests.java
/*
 * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
 * or more contributor license agreements. Licensed under the Elastic License
 * 2.0 and the Server Side Public License, v 1; you may not use this file except
 * in compliance with, at your election, the Elastic License 2.0 or the Server
 * Side Public License, v 1.
 */
package org.elasticsearch.repositories.azure;
import com.azure.storage.common.policy.RequestRetryOptions;
import org.elasticsearch.common.settings.MockSecureSettings;
import org.elasticsearch.common.settings.Settings;
import org.elasticsearch.common.settings.SettingsException;
import org.elasticsearch.common.settings.SettingsModule;
import org.elasticsearch.test.ESTestCase;
import org.elasticsearch.threadpool.TestThreadPool;