Bill Currency Utils For Conversation Support

[mubarak23]

📝 Description

Please provide a brief summary of the changes in this pull request. What issue(s) does this PR address? What problem(s) does it solve?

Relates to #328

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✅ Checklist

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• My code adheres to the coding guidelines of this project.
• I have run cargo fmt.
• I have run cargo clippy.
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🚀 Changes Made

• Other Changes:
  • Add currency utils where we can convert from BTC to SATS
  • Convert a string to a Currency enum
  • Convert a Currency enum to a string

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💡 How to Test

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1. cargo run build

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🤝 Related Issues

List any related issues, pull requests, or discussions:

• Basic Currency Support #328

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• Does the code follow the repository's contribution guidelines?
• Are there any potential bugs or performance issues?
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[mubarak23]

@zupzup kindly review this Draft PR,

am a bit confuse on where to use it in the codebase

[zupzup]

Generally, this looks fine with some changes (I added a few comments).

The BTC to Sat conversion is optional for now, since we don't use it anywhere as of yet.

In terms of where to add it - the validation would need to be added to every place where a sum, or amount with a currency is sent to the Web API (e.g. issue bill).

[zupzup]

This should just take &self and can just return &'static str, it doesn't have to return an Option, since you can cover every case (currently only Currency::Sat).

pub fn as_str(&self) -> &'static str {
  match self {
    Currency::Sat => "sat",
  }
}

[zupzup]

Using f64 for currency conversion is problematic, because floating point ops can introduce precision errors.

To to this correctly, we'd need something like rust-decimal (https://docs.rs/rust_decimal/latest/rust_decimal/) or something similar.

Since we currently send the sum as a string, it would also be OK to convert to a BTC string like "0.100".