[L2] Implement transfer function on gateway for transferring subdomains ownership

[pikonha]

Feature Request

The user should be able to transfer its domains to any given address as long as the ownership is validated.

Describe Preferred Solution

The function signature looks like this:

function transfer(signature: string, address: string, domain: string) : Promise<void>;

This function follows the ERC-712 NFT standard and the underlying implementation should change the domain's owner address to the given one.

The signature is required to validate the ownership of the address before transferring it.