Naming collision with nested enums

# Problem

Currently these two enums in the same file will be both compiled into the same name of `ContentStatus`

```
message Content {enum Status{ ... }}
enum ContentStatus{ ... }
```

Currently the behaviour is to silently overwrite one of the enums, therefore making all subsequent call of the enum possibly wrong.

# Workaround

I have consulted @nat-n and they say they don't see a way to work around the issue currently, except to directly modify the generated code.