tests: add test_execute_message_v5_skip_meta_sets_flag

Before this PR, _SKIP_METADATA_FLAG was never written to the wire — the skip_meta
field existed on _QueryMessage but _write_query_params did not use it.  The PR
activates it for the first time for all protocol versions.

The new test pins the v5 wire encoding: skip_meta=True must produce a 4-byte
flags word of 0x00000003 (VALUES_FLAG | SKIP_METADATA_FLAG), alongside the
always-present result_metadata_id sentinel for v5.

Author: nikagra

tests/unit/test_protocol.py

@@ -82,6 +82,32 @@ def test_execute_message_skip_meta_flag(self):
         # flags byte should be VALUES_FLAG | SKIP_METADATA_FLAG = 0x01 | 0x02 = 0x03
         self._check_calls(mock_io, [(b'\x00\x01',), (b'1',), (b'\x00\x04',), (b'\x03',), (b'\x00\x00',)])
 
+    def test_execute_message_v5_skip_meta_sets_flag(self):
+        """
+        On protocol v5, skip_meta=True must set _SKIP_METADATA_FLAG in the
+        4-byte flags word.  This confirms that _SKIP_METADATA_FLAG is actually
+        written to the wire (it was dead code in upstream before this PR).
+
+        v5 always writes result_metadata_id (None → empty sentinel b'') and uses
+        a 4-byte int for flags instead of a 1-byte field.
+        """
+        message = ExecuteMessage('1', [], 4, skip_meta=True)
+        mock_io = Mock()
+
+        message.send_body(mock_io, 5)
+        # v5 wire layout:
+        #   query_id:           short(1) + b'1'
+        #   result_metadata_id: short(0) + b''  (sentinel — None on init)
+        #   consistency:        short(4) = ONE
+        #   flags (4-byte int): VALUES_FLAG(0x01) | SKIP_METADATA_FLAG(0x02) = 0x03
+        #   param count:        short(0)
+        self._check_calls(mock_io, [
+            (b'\x00\x01',), (b'1',),
+            (b'\x00\x00',), (b'',),
+            (b'\x00\x04',),
+            (b'\x00\x00\x00\x03',), (b'\x00\x00',),
+        ])
+
     def test_execute_message_scylla_metadata_id_v4(self):
         """result_metadata_id should be written on protocol v4 when use_metadata_id=True (Scylla extension)."""
         message = ExecuteMessage('1', [], 4)