Add financial system

[zpano]

Fixes #973

PR Checklist

• [x] Tests
• [ ] Documentation
• [ ] Added entry to CHANGELOG.md
• [ ] Tried the feature on a public network

[ericnordelo]

Hey @zpano, thanks for taking the time to contribute. Note that we expect the PR to contain a strong test suite before reviewing it, and documentation before merging it.

[zpano]

@ericnordelo How can i write an documentation?

[andrew-fleming]

Hey, @zpano! Thanks for opening the PR. Here are the basic guidelines for contributing: https://github.com/OpenZeppelin/cairo-contracts/blob/main/CONTRIBUTING.md

How can i write an documentation?

An example of in-code docs: https://github.com/OpenZeppelin/cairo-contracts/blob/main/src/token/erc20/erc20.cairo#L117-L124

And here's instructions for the docsite: https://github.com/OpenZeppelin/cairo-contracts/blob/main/CONTRIBUTING.md#documentation

Let us know if you have any questions

[immrsd]

Thank you for your contribution! From this point we're going to take over the implementation of Vesting Components, make the necessary changes and bring it to life

[ericnordelo]

Closing as we already merged VestingComponent in #1116