[test-dapp] Introduce Permit Signature on the Test-Dapp

[seaona]

What: 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
  }

How:

• the first part of the work, and the scope of this ticket, 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.