feat: Add TransformSchema message. (#24)

plugin/v3/plugin.proto

@@ -29,6 +29,8 @@ service Plugin {
  rpc Write(stream Write.Request) returns (Write.Response);
  // Transform resources.
  rpc Transform(stream Transform.Request) returns (stream Transform.Response);
+ // Transform schemas.
+ rpc TransformSchema(stream TransformSchema.Request) returns (stream TransformSchema.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
@@ -203,6 +205,17 @@ message Transform {
  }
 }
 
+message TransformSchema {
+ message Request {
+ // marshalled arrow.Schema
+ bytes schema = 1;
+ }
+ message Response {
+ // marshalled arrow.Schema
+ bytes schema = 1;
+ }
+}
+
 message Close {
  message Request {}
  message Response {}