checks added

[yvesbou]

• [x] state updates
• [x] make calls if any
• [x] emit events
• [x] add tests

[yvesbou]

Normal Behavior Tested Add Tests for checks

if (_amount <= 0) {
       revert InsufficientAmount({depositAmount: _amount});
        }

if (!addressToFundingStatus[address(msg.sender)]) {
      // this address has not funded the contract
      revert UserNotAFunder();
      }

if (addressToFunds[address(msg.sender)] < _amount) {
        // the user wanted to withdraw more than deposited
        revert InsufficientBalance({available: addressToFunds[address(msg.sender)], required: _amount});
        }