Nested enum support in Protobuf message

[juha-aiven]

What is currently missing?

An enum embedded in a message is currently not supported:

syntax = "proto3";

package x.y.;
message MyMessage {
  message MyNestedMessage {
    enum MyNestedEnum {
      VALUE_1 = 0;
    }
    MyNestedEnum enum1 = 1;
  }
}

The workaround is to move the nested enum to top level:

syntax = "proto3";

package x.y.;
enum MyNestedEnum {
  VALUE_1 = 0;
}
message MyMessage {
  message MyNestedMessage {
    MyNestedEnum enum1 = 1;
  }
}

How could this be improved?

Add the support.