[L2] RegisterParams improvement

[pikonha]

Feature Request

The registerParams struct can be more complete by adding the following properties making it easier for the frontend to integrate with it.

Describe Preferred Solution

• available: whether the domains is available for registering
• token: EIP-7528 token address enabling ERC-20 payments.

The final struct would look like the following:

struct RegisterParams {
    uint256 price;
    bool available;
    address token;
    uint256 commitTime;
    bytes extraData;
}

QA Replication steps

1. call registerParams
2. receive an available and token properties