Created metadata lib and added AliasMetadataModel and MappingMetadataModel

Signed-off-by: Manik Garg <gargmanik1317@gmail.com>

Author: gargmanik13

CHANGELOG.md

@@ -9,6 +9,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Added public getter method in `SourceFieldMapper` to return excluded field ([#20205](https://github.com/opensearch-project/OpenSearch/pull/20205))
 - Relax jar hell check when extended plugins share transitive dependencies ([#20103](https://github.com/opensearch-project/OpenSearch/pull/20103))
 - Added public getter method in `SourceFieldMapper` to return included field ([#20290](https://github.com/opensearch-project/OpenSearch/pull/20290))
+- Created new metadata lib and added AliasMetadataModel and MappingMetadataModel classes ([#20328](https://github.com/opensearch-project/OpenSearch/pull/20328))
 
 ### Changed
 - Handle custom metadata files in subdirectory-store ([#20157](https://github.com/opensearch-project/OpenSearch/pull/20157))

libs/metadata/build.gradle

@@ -0,0 +1,24 @@
+apply plugin: 'opensearch.publish'
+
+base {
+  archivesName = 'opensearch-metadata'
+}
+
+dependencies {
+    api project(':libs:opensearch-common')
+    api project(':libs:opensearch-core')
+
+    testImplementation "com.carrotsearch.randomizedtesting:randomizedtesting-runner:${versions.randomizedrunner}"
+    testImplementation "junit:junit:${versions.junit}"
+    testImplementation "org.hamcrest:hamcrest:${versions.hamcrest}"
+
+    testImplementation(project(":test:framework")) {
+      exclude group: 'org.opensearch', module: 'opensearch-metadata'
+    }
+}
+
+thirdPartyAudit.enabled = false
+
+tasks.withType(de.thetaphi.forbiddenapis.gradle.CheckForbiddenApis) {
+    enabled = false
+}

libs/metadata/src/main/java/org/opensearch/metadata/compress/CompressedData.java

@@ -0,0 +1,90 @@
+/*
+ * 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.metadata.compress;
+
+import org.opensearch.common.annotation.ExperimentalApi;
+import org.opensearch.core.common.io.stream.StreamInput;
+import org.opensearch.core.common.io.stream.StreamOutput;
+import org.opensearch.core.common.io.stream.Writeable;
+
+import java.io.IOException;
+import java.util.Arrays;
+
+/**
+ * Generic data holder class for compressed data.
+ * This class stores compressed bytes and their checksum.
+ * <p>
+ * Can be used for any type of compressed content (XContent, raw bytes, etc.)
+ */
+@ExperimentalApi
+public final class CompressedData implements Writeable {
+
+    private final byte[] compressedBytes;
+    private final int checksum;
+
+    /**
+     * Creates a new CompressedData object.
+     *
+     * @param compressedBytes the compressed bytes
+     * @param checksum        the checksum of the uncompressed content
+     */
+    public CompressedData(byte[] compressedBytes, int checksum) {
+        this.compressedBytes = compressedBytes;
+        this.checksum = checksum;
+    }
+
+    /**
+     * Creates a new CompressedData object from a stream.
+     *
+     * @param in the stream input
+     * @throws IOException if an I/O error occurs
+     */
+    public CompressedData(StreamInput in) throws IOException {
+        this.checksum = in.readInt();
+        this.compressedBytes = in.readByteArray();
+    }
+
+    /**
+     * Returns the compressed bytes.
+     *
+     * @return the compressed bytes
+     */
+    public byte[] compressedBytes() {
+        return compressedBytes;
+    }
+
+    /**
+     * Returns the checksum of the uncompressed content.
+     *
+     * @return the checksum value
+     */
+    public int checksum() {
+        return checksum;
+    }
+
+    @Override
+    public void writeTo(StreamOutput out) throws IOException {
+        out.writeInt(checksum);
+        out.writeByteArray(compressedBytes);
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+
+        CompressedData that = (CompressedData) o;
+        return checksum == that.checksum && Arrays.equals(compressedBytes, that.compressedBytes);
+    }
+
+    @Override
+    public int hashCode() {
+        return checksum;
+    }
+}

libs/metadata/src/main/java/org/opensearch/metadata/compress/package-info.java

@@ -0,0 +1,10 @@
+/*
+ * 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.
+ */
+
+/** Compression package. */
+package org.opensearch.metadata.compress;