Implementation of 'Flow Cancel' modifications to Governor calculations #3798

- Add an allow list of tokens to be used in the Flow Cancel design

Adds an implementation of 'flow canceling' logic into the Governor: - There now exists an allow-list of 'flow cancel tokens' - When calculating the governor usage for some emitting chain, its usage is now decrementing by the sum of all transfers from other chains that use flow-canceling tokens and have their destination chain equal to emitting chain in question - In effect, TrimAndSumValue now calculates the net Usage of a chain when flow canceling is taken into account - This commit also adds a basic unit test demonstrating flow cancelling for a simple case

1. Add check to ensure that now underflow is possible when the sum of flow cancelling transactions is greater than the sum of all transfers from the emitter chain 2. Ensure that the sum of all transfers from an emitter chain does not exceed the dailyLimit of a Governor. This is done by testing against a specific error message and ensuring that it is returned by the program when we force it into this illegal state

- Remove most of the unused field from the flow cancel token list to make it easier to grok - Clarify in the source code that the tokens are taken directly from the generated mainnet token list - Move comments around in the governor code to make them easier to read - Make varible name extra verbose and easier to understand

Hard-coded value should be 1, not 2, because we are only summing over the emitter chain's transfers

Use the concept of a 'negative transfer' to represent flow-cancelling. This required the following modifications: - Add wrapped struct around db.Transfer that includes a int64 value for negative calcuations. It is used only by the Governor for these calculations `chainEntry` struct - modify to use the wrapped struct that includes int64 value - Added comments to clarify the purpose of transfers with negative values `tokenEntry` struct - modify to use a `flowCancel` boolean that marks whether incoming transfers of this asset should reduce the Governor limit for the Target chain `TrimAndSumValue` function - Modify to return signed integer - ensure it cannot go below 0 (underflow). Instead, negative sums will just return 0 to signal that the Governor has no 'usage' in the sense of the rate-limiting budget. In general, calling code and function signatures were modified to accept the new transfer type and signed integers instead of unsigned where necessary. This commit also adds validation functions that make it easier to add flow cancelling transfers to a chainEntry. It also adds two 'checked math' functions in the style of Rust to allow for easier overflow checking.

Also remove commented code from a previous commit

also cleanup comments

- Add a comment to the helper method to mention that the calling code is responsible for verifying that a flow cancel asset should actually flow cancel. (This is done via the `tokens` property in the Governor struct - Add comments to calling code mentioning that the verification is necessary - Modify the unit tests to perform this verification

Added Solana testnet USDC to the config for devnet and testnet Address sourced from Circle docs: https://developers.circle.com/stablecoins/docs/usdc-on-test-networks

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Implementation of 'Flow Cancel' modifications to Governor calculations #3798

Implementation of 'Flow Cancel' modifications to Governor calculations #3798

Commits on Jun 4, 2024