rbx_types Variant::String should be backed by Vec<u8> instead of String

[kennethloeffler]

Right now, rbx_types uses the Rust String type to represent Roblox string values. This works most of the time, but is actually incorrect because Roblox strings are not required to be UTF-8. So, rbx-dom is currently unable to losslessly decode files that have non UTF-8 string properties.

The idea of using the bstr crate has been thrown around before, but after a bit of investigation, this won't work very well because BString's human-readable serde representation is always a list of numbers, which makes rbx-dom's various snapshot tests unreadable, and which will seriously bloat the JSON representation. We also cannot provide our own Serialize/Deserialize implementations for BString because of the orphan rule. We could just newtype it... but this somewhat nullifies the benefits of pulling in a crate!

So, to put the nail in the coffin on this, I'm thinking we'll have change rbx-dom's String variant so it is backed by a type that contains either a Vec<u8> or a String, perhaps called RobloxString or something.

Lastly, we've just had breaking changes to rbx_dom_weak. Breaking 2 different crates in rbx-dom at once might be a bit much to take on right now since we'll already have to make some fairly sweeping changes to Rojo, so this should probably wait until after rbx-dom's next batch of releases.

[kennethloeffler]

Lastly, we've just had breaking changes to rbx_dom_weak. Breaking 2 different crates in rbx-dom at once might be a bit much to take on right now since we'll already have to make some fairly sweeping changes to Rojo, so this should probably wait until after rbx-dom's next batch of releases.

Or, we might leave Variant::String alone, and just add RobloxString and change the types of Instance.name and InstanceBuilder.name to it for now, since we're breaking rbx_dom_weak anyway?

Scratch that, we'll need to do it all at once because of how serialization works in rbx_binary and rbx_xml

Scratch that (again) - we would be able to change the types of Instance.name and InstanceBuilder.name to RobloxString, and could deserialize instance names just fine without touching Variant::String, but would have to perform a lossy conversion for instance names during serialization, and also perform a lossy conversion for other string properties during both serialization and deserialization.