Token approvals knowledge base

https://support.metamask.io/hc/en-us/articles/6174898326683-What-is-a-token-approval-

https://info.etherscan.com/tokenapprovals/

https://ethereum.org/en/developers/tutorials/transfers-and-approval-of-erc-20-tokens-from-a-solidity-smart-contract/

https://www.linkedin.com/pulse/erc20-decoded-understanding-approvals-allowances-frederick-van-staden/

https://ethereum.stackexchange.com/questions/129681/approval-and-transfer-from-function-in-erc-20-tokens

https://medium.com/frak-defi/erc-2612-the-ultimate-guide-to-gasless-erc-20-approvals-2cd32ddee534

https://eips.ethereum.org/EIPS/eip-2612

https://blog.uniswap.org/permit2-and-universal-router