Add support for Azure US Government (#207)

Co-authored-by: Marcin Patalon <[email protected]>

Author: mpatalon

src/main/java/org/jenkinsci/plugins/azurekeyvaultplugin/AzureKeyVaultCredentialRetriever.java

@@ -35,6 +35,7 @@ public static TokenCredential getCredentialById(String credentialID, Run<?, ?> b
             CredentialsProvider.track(build, cred);
             AzureCredentials azureCredentials = (AzureCredentials) cred;
             credential = new ClientSecretCredentialBuilder()
+                    .authorityHost(azureCredentials.getAzureEnvironment().getActiveDirectoryEndpoint())
                     .clientId(azureCredentials.getClientId())
                     .clientSecret(azureCredentials.getPlainClientSecret())
                     .httpClient(HttpClientRetriever.get())