Implement Transform function in Plugin proto file. (#23)

plugin/v3/plugin.proto

@@ -27,6 +27,8 @@ service Plugin {
  rpc Read(Read.Request) returns (stream Read.Response);
  // Write resources. Write is the mirror of Sync, expecting a stream of messages as input.
  rpc Write(stream Write.Request) returns (Write.Response);
+ // Transform resources.
+ rpc Transform(stream Transform.Request) returns (stream Transform.Response);
  // Send signal to flush and close open connections
  rpc Close(Close.Request) returns (Close.Response);
  // Validate and test the connections used by the plugin
@@ -190,6 +192,17 @@ message Write {
  message Response {}
 }
 
+message Transform {
+ message Request {
+ // marshalled arrow.Record
+ bytes record = 1;
+ }
+ message Response {
+ // marshalled arrow.Record
+ bytes record = 1;
+ }
+}
+
 message Close {
  message Request {}
  message Response {}