Add licensing

[farshidtz]

The project has no licensing. Ideally, this needs to be a loyalty free license to easily allow the use of the program in other snaps.

However, this isn't possible right now, given that the Rust code uses the following libraries:

• https://crates.io/crates/dotenv (MIT)
• https://docs.rs/http-body-util/latest/http_body_util/index.html (MIT)
• https://github.com/hyperium/hyper (MIT)
• https://github.com/hyperium/hyper-util (MIT)
• https://github.com/softprops/hyperlocal (MIT)
• https://github.com/serde-rs/serde (Apache 2.0 or MIT)
• https://docs.rs/serde_json/latest/serde_json/ (Apache 2.0 or MIT)
• https://github.com/tokio-rs/tokio (MIT)

[locnnil]

The MIT license isn't a viral license like GPLv3, GPLv3+, or later versions. In fact, it's quite the opposite; MIT is a permissive license, similar to Apache 2.0 and BSD.

This means that: just because the libraries are licensed under MIT doesn't mean that the application's code must be MIT as well. We can choose to license the project under another permissive license if we wish. Our only obligation is to acknowledge that we're using libraries that are licensed under MIT.

[farshidtz]

Our only obligation is to acknowledge that we're using libraries that are licensed under MIT.

That's exactly the problem. Every snap using the current Rust program needs to list MIT as one of its licenses, and provide the license text for it.