Introducing Permit Signature

[seaona]

What: in this PR we are introducing a specific Typed Data V4 signature: Permit. According to the specs for EIP-2612, the signature will have a data type Permit with the following data fields:

  "message": {
    "owner": owner,
    "spender": spender,
    "value": value,
    "nonce": nonce,
    "deadline": deadline
  }

permit.mp4

• Fixes [test-dapp] Introduce Permit Signature on the Test-Dapp metamask-extension#17941

How:

• the first part of the work, and the scope of this PR, consists in introducing a Permit signature.
• a future PR will take care of importing an ERC20 Permit contract which implements the permit signature, and complete the flow by adding the functionality of executing the Permit and seeing how allowance is increased only by signing a Permit signature.
• the signature split of v, r and s fields in this PR is a preparatory work, that would be needed for the future PR