Feature Request: Option to add user-defined prefixes to generated types

[Aderinom]

I'd like to request an option which allows to prepend a user-defined prefix to generated message struct names.

In multi-protocol systems, it is common to maintain a canonical model for shared types. To avoid naming collisions between generated message types from different domains or protocols, it would be useful to support a configurable prefix for generated Rust message structs.

Example:

message User {}

Without a prefix:

struct User

With a prefix such as Rpc:

struct RpcUser