Enabled automated license header checks

1. Added the SPDX license header to the files with missing license headers.
2. Re-enabled the 'licenseHeaders' check in the build.gradle file.
3. Added an IntelliJ copyright profile to auto-generate the SPDX license header.
4. Updated the .gitignore file.

Signed-off-by: Ketan Verma <ketan9495@gmail.com>

.gitignore

@@ -0,0 +1,32 @@
+# Compiled class file
+*.class
+
+# Log file
+*.log
+
+# BlueJ files
+*.ctxt
+
+# Mobile Tools for Java (J2ME)
+.mtj.tmp/
+
+# virtual machine crash logs, see http://www.java.com/en/download/help/error_hotspot.xml
+hs_err_pid*
+
+# IntelliJ files
+.idea/*
+*.iml
+*.ipr
+*.iws
+build-idea/
+out/
+
+# Include Copyright template for IntelliJ
+!.idea/copyright
+
+# Gradle files
+.gradle
+build
+
+# OSX files
+.DS_Store

build.gradle

@@ -113,8 +113,7 @@ tasks.named("integTest").configure {
     it.dependsOn(project.tasks.named("bundlePlugin"))
 }
 
-//TODO enable license headers
-licenseHeaders.enabled = false
+licenseHeaders.enabled = true
 dependencyLicenses.enabled = false
 thirdPartyAudit.enabled = false
 validateNebulaPom.enabled = false

src/main/java/org/opensearch/search/asynchronous/settings/LegacyOpendistroAsynchronousSearchSettings.java

@@ -1,3 +1,14 @@
+/*
+ * 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.
+ *
+ * Modifications Copyright OpenSearch Contributors. See
+ * GitHub history for details.
+ */
+
 package org.opensearch.search.asynchronous.settings;
 
 import org.opensearch.common.settings.Setting;

src/test/java/org/opensearch/search/asynchronous/settings/AsynchronousSearchSettingsTests.java

@@ -1,3 +1,14 @@
+/*
+ * 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.
+ *
+ * Modifications Copyright OpenSearch Contributors. See
+ * GitHub history for details.
+ */
+
 package org.opensearch.search.asynchronous.settings;
 
 import org.junit.Before;

src/test/java/org/opensearch/search/asynchronous/utils/QuadConsumer.java

@@ -1,3 +1,14 @@
+/*
+ * 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.
+ *
+ * Modifications Copyright OpenSearch Contributors. See
+ * GitHub history for details.
+ */
+
 /*
  *   Copyright 2020 Amazon.com, Inc. or its affiliates. All Rights Reserved.
  *
@@ -12,16 +23,6 @@
  *   express or implied. See the License for the specific language governing
  *   permissions and limitations under the License.
  */
-/*
- * 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.
- *
- * Modifications Copyright OpenSearch Contributors. See
- * GitHub history for details.
- */
 
 package org.opensearch.search.asynchronous.utils;