DBZ-6637 Fix case concern with Db2

src/main/java/io/debezium/connector/jdbc/dialect/db2/Db2DatabaseDialect.java

@@ -153,4 +153,18 @@ public String getFormattedTimestampWithTimeZone(String value) {
         return String.format("'%s'", DateTimeFormatter.ISO_LOCAL_DATE_TIME.format(zonedDateTime));
     }
 
+    @Override
+    protected String resolveColumnNameFromField(String fieldName) {
+        String columnName = super.resolveColumnNameFromField(fieldName);
+        if (!getConfig().isQuoteIdentifiers()) {
+            // There are specific use cases where we explicitly quote the column name, even if the
+            // quoted identifiers is not enabled, such as the Kafka primary key mode column names.
+            // If they're quoted, we shouldn't uppercase the column name.
+            if (!getIdentifierHelper().toIdentifier(columnName).isQuoted()) {
+                // Db2 defaults to uppercase for identifiers
+                columnName = columnName.toUpperCase();
+            }
+        }
+        return columnName;
+    }
 }