UUNSE - Audit

One or more declarations do not conform to the [Solidity style guide](https://solidity.readthedocs.io/en/v0.7.3/style-guide.html#naming-conventions) with regards to its naming convention. Particularly: - `camelCase`: Should be applied to function names, argument names, local and state variable names, modifiers - `UPPER_CASE`: Should be applied to `constant` variables - `CapWords`: Should be applied to contract names, struct names, event names and enums Constant variable `_maxSupply` is not in `UPPER_CASE`: ```solidity=345 uint256 private constant _maxSupply = 10000000000 * 1e18; ```

The functions which are never called internally within the contract should have external visibility for gas optimization.

It is highly recommended NOT to include OpenZeppelin library code directly in source code, but import the original library to minimize risk because even slight changes to the library code may lead to critical/major vulnerabilities/bugs. The latest version of the OpenZeppelin libraries is 4.7.3.

The `approve` function could be used in an attack that allows a spender to transfer more tokens than the owner of the tokens ever wanted to allow the spender to transfer. Here is a possible attack scenario: Alice allows Bob to transfer N of Alice's tokens (N>0) by calling approve method on token smart contract passing Bob's address and N as method arguments. After some time, Alice decides to change from N to M (M>0) the number of Alice's tokens Bob is allowed to transfer, so she calls `approve()` method again, this time passing Bob's address and M as method arguments. Bob notices Alice's second transaction before it was mined and quickly sends another transaction that calls `transferFrom()` method to transfer N Alice's tokens somewhere. If Bob's transaction will be executed before Alice's transaction, then Bob will successfully transfer N Alice's tokens and will gain the ability to transfer another M tokens. Before Alice noticed that something went wrong, Bob calls `transferFrom()` method again, this time to transfer M Alice's tokens. So, Alice's attempt to change Bob's allowance from N to M (N>0 and M>0) made it possible for Bob to transfer N+M of Alice's tokens, while Alice never wanted to allow so many of her tokens to be transferred by Bob. ERC20 API: An Attack Vector on Approve/TransferFrom Methods: https://docs.google.com/document/d/1YLPtQxZu1UAvO9cZ1O2RPXBbT0mooh4DYKjA_jp-RLM/edit#heading=h.m9fhqynw2xvt

The linked statements do not affect the functionality of the codebase and appear to be either leftovers from test code or older functionality.

Literals with many digits are difficult to read and review. ```solidity=345 uint256 private constant _maxSupply = 10000000000 * 1e18; ```

Variables `_name`, `_symbol` and `_decimals` could be declared as `constant` since these state variables are hardcoded in the constructor and never to be changed.

The linked variables assigned in the constructor can be declared as `immutable`. Immutable state variables can be assigned during contract creation but will remain constant throughout the lifetime of a deployed contract. A big advantage of immutable variables is that reading them is significantly cheaper than reading from regular state variables since they will not be stored in storage.