feat: make DefaultLogicalExtensionCodec support serialisation of buil…

datafusion/proto/proto/datafusion.proto

@@ -270,6 +270,25 @@ message CopyToNode {
   repeated string partition_by = 7;
 }
 
+// Identifies a built-in file format supported by DataFusion.
+// Used by DefaultLogicalExtensionCodec to serialize/deserialize
+// FileFormatFactory instances (e.g. in CopyTo plans).
+enum FileFormatKind {
+  FILE_FORMAT_KIND_UNSPECIFIED = 0;
+  FILE_FORMAT_KIND_CSV = 1;
+  FILE_FORMAT_KIND_JSON = 2;
+  FILE_FORMAT_KIND_PARQUET = 3;
+  FILE_FORMAT_KIND_ARROW = 4;
+  FILE_FORMAT_KIND_AVRO = 5;
+}
+
+// Wraps a serialized FileFormatFactory with its format kind tag,
+// so the decoder can dispatch to the correct format-specific codec.
+message FileFormatProto {
+  FileFormatKind kind = 1;
+  bytes encoded_file_format = 2;
+}
+
 message DmlNode{
    enum Type {
     UPDATE = 0;