Make from_toml_value case sensitive

[epilys]

TOML is case sensitive [0], so key values should not be lowercased.

[0] https://github.com/toml-lang/toml#user-content-spec

[mehcode]

🙇‍♂️ Thank you for your contribution. However, I do not wish to accept any breaking changes to this repository at this time.

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Note that I fully agree with changing this but it will be a part of #111.

[epilys]

Note that I fully agree with changing this

I don't know if it's a matter of agreeing or not, since it's in the specification and now config-rs isn't compliant. It's a bug.

But of course it's your decision and I respect it.

EDIT; I misread the part I quoted! Apologies. :D But still, for my usage at least, it's a bug and I will have to use a forked version.

[mehcode]

@epilys Let me try and explain my reasoning here as its not completely a bug.

config has been about merging different sources of configuration with the most common example being a file and the environment.

To make this merging process "easy", all configuration keys were lowercased when they entered the configuration store.

In hindsight that was not ideal. However, I can't remove the lowercasing without allowing for case-insensitive merging of configuration keys which is now depended on by several projects (mine included). The current solution for this is that in v0.10 configuration keys will be stored as received (no lowercasing) but all comparison operations will be done using case folding.