Add missing license header (opensearch-project#3467)

Added missing license header for some files.

- [ ] New functionality includes testing
- [ ] New functionality has been documented
- [ ] Commits are signed per the DCO using --signoff

By submitting this pull request, I confirm that my contribution is made
under the terms of the Apache 2.0 license.
For more information on following Developer Certificate of Origin and
signing off your commits, please check
[here](https://github.com/opensearch-project/OpenSearch/blob/main/CONTRIBUTING.md#developer-certificate-of-origin).

Signed-off-by: Andrey Pleskach <[email protected]>
(cherry picked from commit fb82bbb)

src/integrationTest/java/org/opensearch/test/framework/testplugins/AbstractRestHandler.java

@@ -1,12 +1,12 @@
 /*
-* Copyright OpenSearch Contributors
-* SPDX-License-Identifier: Apache-2.0
-*
-* The OpenSearch Contributors require contributions made to
-* this file be licensed under the Apache-2.0 license or a
-* compatible open source license.
-*
-*/
+ * Copyright OpenSearch Contributors
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ *
+ */
 package org.opensearch.test.framework.testplugins;
 
 import org.opensearch.ExceptionsHelper;

src/main/java/org/opensearch/security/dlic/rest/validation/EndpointValidator.java

@@ -1,12 +1,12 @@
 /*
-* Copyright OpenSearch Contributors
-* SPDX-License-Identifier: Apache-2.0
-*
-* The OpenSearch Contributors require contributions made to
-* this file be licensed under the Apache-2.0 license or a
-* compatible open source license.
-*
-*/
+ * Copyright OpenSearch Contributors
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ *
+ */
 package org.opensearch.security.dlic.rest.validation;
 
 import org.opensearch.core.rest.RestStatus;
@@ -113,6 +113,7 @@ default ValidationResult<SecurityConfiguration> entityStatic(final SecurityConfi
         final var configuration = securityConfiguration.configuration();
         final var entityName = securityConfiguration.entityName();
         if (configuration.isStatic(entityName)) {
+
             return ValidationResult.error(RestStatus.FORBIDDEN, forbiddenMessage("Resource '" + entityName + "' is static."));
         }
         return ValidationResult.success(securityConfiguration);
@@ -131,6 +132,7 @@ default ValidationResult<SecurityConfiguration> entityHidden(final SecurityConfi
         final var configuration = securityConfiguration.configuration();
         final var entityName = securityConfiguration.entityName();
         if (configuration.isHidden(entityName)) {
+
             return ValidationResult.error(RestStatus.NOT_FOUND, notFoundMessage("Resource '" + entityName + "' is not available."));
         }
         return ValidationResult.success(securityConfiguration);
@@ -158,6 +160,7 @@ default ValidationResult<SecurityConfiguration> isAllowedToChangeEntityWithRestA
             final var configuration = securityConfiguration.configuration();
             final var existingEntity = configuration.getCEntry(securityConfiguration.entityName());
             if (restApiAdminPrivilegesEvaluator().containsRestApiAdminPermissions(existingEntity)) {
+
                 return ValidationResult.error(RestStatus.FORBIDDEN, forbiddenMessage("Access denied"));
             }
         } else {
@@ -167,6 +170,7 @@ default ValidationResult<SecurityConfiguration> isAllowedToChangeEntityWithRestA
                 configuration.getImplementingClass()
             );
             if (restApiAdminPrivilegesEvaluator().containsRestApiAdminPermissions(configEntityContent)) {
+
                 return ValidationResult.error(RestStatus.FORBIDDEN, forbiddenMessage("Access denied"));
             }
         }

src/test/java/org/opensearch/security/dlic/rest/api/AccountApiActionConfigValidationsTest.java

@@ -1,12 +1,12 @@
 /*
-* Copyright OpenSearch Contributors
-* SPDX-License-Identifier: Apache-2.0
-*
-* The OpenSearch Contributors require contributions made to
-* this file be licensed under the Apache-2.0 license or a
-* compatible open source license.
-*
-*/
+ * Copyright OpenSearch Contributors
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ *
+ */
 package org.opensearch.security.dlic.rest.api;
 
 import com.fasterxml.jackson.databind.node.ObjectNode;

src/test/java/org/opensearch/security/dlic/rest/api/ActionGroupsApiActionValidationTest.java

@@ -1,12 +1,12 @@
 /*
-* Copyright OpenSearch Contributors
-* SPDX-License-Identifier: Apache-2.0
-*
-* The OpenSearch Contributors require contributions made to
-* this file be licensed under the Apache-2.0 license or a
-* compatible open source license.
-*
-*/
+ * Copyright OpenSearch Contributors
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ *
+ */
 package org.opensearch.security.dlic.rest.api;
 
 import org.junit.Before;

src/test/java/org/opensearch/security/transport/SecuritySSLRequestHandlerTests.java

@@ -1,3 +1,12 @@
+/*
+ * Copyright OpenSearch Contributors
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ *
+ */
 package org.opensearch.security.transport;
 
 import org.junit.Assert;