#28059 Improving duplicated variables handling. (#28421)

* #28059 Improving duplicated variables handling.

* #28059 Refactor HostVariableAPIImpl to use ImmutableList

The HostVariableAPIImpl was refactored to make use of Google's Immutable List implementation for returned site variables in the getUniqueSiteVariables() method. We previously used an ArrayList, but have made the shift for its immutable properties and thread-safety.

dotCMS/src/main/java/com/dotmarketing/portlets/hostvariable/bussiness/HostVariableAPIImpl.java

@@ -11,13 +11,15 @@
 import com.dotmarketing.exception.DotSecurityException;
 import com.dotmarketing.portlets.contentlet.business.HostAPI;
 import com.dotmarketing.portlets.hostvariable.model.HostVariable;
+import com.google.common.collect.ImmutableList;
 import com.liferay.portal.language.LanguageException;
 import com.liferay.portal.model.User;
 import java.util.ArrayList;
 import java.util.Comparator;
 import java.util.Date;
 import java.util.List;
 import java.util.Optional;
+import java.util.stream.Collectors;
 
 public class HostVariableAPIImpl implements HostVariableAPI {
 
@@ -106,15 +108,17 @@ public List<HostVariable> save(final List<HostVariable> siteVariables, final Str
 			);
 		}
 
-		List<HostVariable> processedVariables = new ArrayList<>();
+		// Removing duplicates from the given list of variables
+		final var uniqueSiteVariables = getUniqueSiteVariables(siteVariables);
 
-		// First we need to get all the existing variables for the host
+		// Getting all the existing variables for the host
 		final List<HostVariable> existingVariables = getVariablesForHost(
 				siteId, user, respectFrontendRoles
 		);
 
 		// Now we need to loop through the new variables save/update them
-		for (HostVariable siteVariable : siteVariables) {
+		List<HostVariable> processedVariables = new ArrayList<>();
+		for (HostVariable siteVariable : uniqueSiteVariables) {
 
 			final HostVariable toProcess;
 
@@ -157,6 +161,23 @@ public List<HostVariable> save(final List<HostVariable> siteVariables, final Str
 		return processedVariables;
 	}
 
+	/**
+	 * Retrieves a list of unique site variables from the given list of site variables.
+	 *
+	 * @param siteVariables The list of site variables.
+	 * @return A new ArrayList containing only the unique site variables based on their keys.
+	 */
+	private List<HostVariable> getUniqueSiteVariables(List<HostVariable> siteVariables) {
+
+		return ImmutableList.copyOf(siteVariables.stream().
+				collect(Collectors.toMap(
+						HostVariable::getKey, // key is the HostVariable's `key`
+						hostVariable -> hostVariable,  // value is the HostVariable itself
+						(existing, replacement) -> existing)) // if there's a conflict, keep the existing
+				.values()
+		);
+	}
+
 	/**
 	 * Checks if two HostVariables are equal based on their key, value, name, and id attributes.
 	 *