_ERC721 token with pausable token transfers, minting and burning.
Useful for scenarios such as preventing trades until the end of an evaluation period, or having an emergency switch for freezing all token transfers in the event of a large bug._
function _beforeTokenTransfer(bytes32 from, bytes32 to, uint256 tokenId) internal virtual
- the contract must not be paused._
This empty reserved space is put in place to allow future versions to add new variables without shifting down storage in the inheritance chain. See https://docs.openzeppelin.com/contracts/4.x/upgradeable#storage_gaps We use a standard of 50 storage slots. The amount referenced below is based on: 50 - numberOfClassMemberVariables.