Avoid ConcurrentModificationException for User class fields (opensearch-project#5087)

Signed-off-by: shikharj05 <8859327+shikharj05@users.noreply.github.com>
Signed-off-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

Author: opensearch-trigger-bot[bot]

src/main/java/org/opensearch/security/securityconf/ConfigModelV7.java

@@ -292,7 +292,10 @@ private Set<String> map(final User user, final TransportAddress caller) {
                 return Collections.emptySet();
             }
 
-            final Set<String> securityRoles = new HashSet<>(user.getSecurityRoles());
+            final Set<String> securityRoles = new HashSet<>();
+            synchronized (user.getSecurityRoles()) {
+                securityRoles.addAll(user.getSecurityRoles());
+            }
 
             if (rolesMappingResolution == ConfigConstants.RolesMappingResolution.BOTH
                 || rolesMappingResolution == ConfigConstants.RolesMappingResolution.BACKENDROLES_ONLY) {