Build a simple lending protocol that allows users to lend and borrow ERC20 tokens. The contract should have the following functions:

- deposit(address _token, uint256 _amount): Allows a user to deposit a specific amount of an ERC20 token into the contract as collateral.
- borrow(address _token, uint256 _amount): Allows a user to borrow a specific amount of an ERC20 token from the contract.
- repay(address _token, uint256 _amount): Allows a user to repay a specific amount of an ERC20 token to the contract.

The contract should also have the following features:

- It should keep track of the total supply of each ERC20 token in the contract, as well as the total amount borrowed and the total amount of collateral.
- It should allow users to borrow a maximum of 80% of the value of their collateral.
- It should implement a liquidation mechanism to recover collateral if the value of the borrowed tokens drops below a certain threshold.
- It should implement the ERC20 interface to allow for compatibility with other ERC20 contracts.

Notes:

- The contract should be written in Solidity and be compatible with the latest version of the Ethereum Virtual Machine (EVM).
- You should provide clear and concise documentation for each function in the contract.
- You should also write unit tests to ensure the contract is functioning correctly