refactor(plc4j/code-gen): Refactored the way Encoding is handled and …

…added "nullBytesHex" attribute support.

- Changed the string-handling to not use an explicit "encoding" method attribute and moved that to using "WithEncoding" options.
- Added support for a new "nullByteHex" attribute for optional fields
- Added an accessor to the readBuffer instance for DataReaders
- Added an accessor to the writeBuffer instance for DataWriters
- Bumped plc4x-code-generation version to 1.7.0-SNAPSHOT

plc4j/drivers/s7/src/main/java/org/apache/plc4x/java/s7/readwrite/utils/StaticHelper.java

@@ -31,6 +31,7 @@
 import org.apache.plc4x.java.s7.readwrite.DataTransportErrorCode;
 import org.apache.plc4x.java.s7.readwrite.ModeTransitionType;
 import org.apache.plc4x.java.s7.utils.S7DiagnosticEventId;
+import org.apache.plc4x.java.spi.codegen.WithOption;
 import org.apache.plc4x.java.spi.generation.ParseException;
 import org.apache.plc4x.java.spi.generation.ReadBuffer;
 import org.apache.plc4x.java.spi.generation.SerializationException;
@@ -1932,9 +1933,9 @@ public static void serializeTiaDateTime(WriteBuffer io, PlcValue value) {
 
     public static String parseS7Char(ReadBuffer io, String encoding) throws ParseException {
         if ("UTF-8".equalsIgnoreCase(encoding)) {
-            return io.readString(8, encoding);
+            return io.readString(8, WithOption.WithEncoding(encoding));
         } else if ("UTF-16".equalsIgnoreCase(encoding)) {
-            return io.readString(16, encoding);
+            return io.readString(16, WithOption.WithEncoding(encoding));
         } else {
             throw new PlcRuntimeException("Unsupported encoding");
         }