add transform

Author: lalitb

opentelemetry-proto/src/transform/metrics.rs

@@ -149,6 +149,7 @@ pub mod tonic {
                 name: metric.name.to_string(),
                 description: metric.description.to_string(),
                 unit: metric.unit.as_str().to_string(),
+                metadata: vec![], // internal and currently unused
                 data: metric.data.as_any().try_into().ok(),
             }
         }