Invoice Dashboard should check if user's wallet has sufficient funds before prompting for approval

[MantisClone]

Problem

The Invoice Dashboard will prompt the user to approve their ERC20 token even if they do not have sufficient Gas or ERC20 token balance to pay the invoice.

Solution

It should check the user's native token balance and ERC20 balance before prompting approval.

Considerations

When estimating gas, consider making it a warning only - don't block users who wish to use a low priority fee.