Rust const string calls function at compile time

For this thrift:

const string broker_playback_message = "mmi.developer.playback"

Generates:

// thrift -gen rs -out ../rust/thrift/src const_string.thrift

pub const BROKER_PLAYBACK_MESSAGE: String = "mmi.developer.playback".to_owned();

Fails to compile:

error[E0015]: calls in constants are limited to tuple structs and tuple variants
note: a limited form of compile-time function evaluation is available on a nightly compiler via `const fn`

Fix:

Probably want to output:

pub const BROKER_PLAYBACK_MESSAGE: &str = "mmi.developer.playback";

Looking at render_const_value() it looks like byte arrays will have the same issue.