feat: vat deploy instructions

src/SampleVat.s.sol

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+// SPDX-License-Identifier: MIT
+pragma solidity 0.8.19;
+
+import "forge-std/Script.sol";
+import {SampleVat} from "./SampleVat.sol";
+
+contract SampleVatDeploy is Script {
+    function run() external returns (SampleVat) {
+        vm.startBroadcast();
+
+        SampleVat tpl = new SampleVat();
+
+        vm.stopBroadcast();
+
+        return tpl;
+    }
+}

vat_guide.md

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+# Minimal `Vat` setup
+
+## Setup localchain using GETH
+
+```bash
+geth --datadir ~/.temp/ --dev --http --http.api web3,eth,debug,net --http.corsdomain "*" --http.vhosts "*" --http.addr 127.0.0.1 --ws --ws.api eth,net,debug,web3 --ws.addr 127.0.0.1 --ws.origins "*" --graphql --graphql.corsdomain "*" --graphql.vhosts "*" --vmdebug
+```
+
+## Setup local environment variables
+
+export ETH_FROM=0x
+export FOUNDRY_ETH_FROM=$ETH_FROM
+export ETHERSCAN_API_KEY=""
+export POLYGONSCAN_API_KEY=""
+export ETH_KEYSTORE="/Users/johndoe/temp/keystore"
+export FOUNDRY_ETH_KEYSTORE_DIR=$ETH_KEYSTORE
+export ETH_PASSWORD="$ETH_KEYSTORE/passwd.txt"
+export FOUNDRY_ETH_PASSWORD_FILE=$ETH_PASSWORD
+
+
+## Deploy `Vat`
+
+0. Deploy `Vat` from `vat.sol`
+
+Example:
+
+```bash
+forge-script.sh ../src/SampleVat.s.sol:SampleVatDeploy --fork-url=$RPC_URL --broadcast -vvvv
+```
+
+## Deploy your ERC-20 token `$CENT`
+
+0. Deploy an ERC-20 that you control
+
+
+
+## Deploy `GemJoin`
+
+0. Deploy a `GemJoin` contract from `join.sol`
+    ```solidity
+    GemJoin(address vat, bytes32 ilk, address gem)
+    ```
+    - `vat`: `<vat_addr>`
+    - `ilk`: `'CENT-A'`
+    - `gem`: `$CENT` ERC20 token address
+
+## Deploy your own "Dai" token `$DAI`
+
+0. Deploy an ERC-20 that you control
+
+Example:
+
+```bash
+forge-script.sh ../src/Cent.s.sol:CenturionDaiDeploy --fork-url=$RPC_URL --broadcast -vvvv
+```
+
+## Authorize the contracts on the `Vat`:
+
+0. `rely` on both join contracts:
+    ```solidity
+    vat.rely(<gem_join_addr>);
+    vat.rely(<dai_join_addr>);
+    ```
+
+## Deploy `DaiJoin`
+
+0. Deploy a `DaiJoin` contract from `join.sol`
+    ```solidity
+    DaiJoin(address vat, address dai)
+    ```
+    - `vat`: `<vat_addr>`
+    - `gem`: `$MYDAI` ERC20 token address
+1. Allow `DaiJoin` to **mint** `$MYDAI`
+1. Allow `DaiJoin` to **burn** `$MYDAI`
+
+## Initialize the collateral type
+
+1. Initialize Vat for `CENT-A`
+    ```solidity
+    vat.init('CENT-A');
+    ```
+2. Set the global debt ceiling `Line` (with capital `L`)
+    ```solidity
+    vat.file('Line', 1_000_000 * 10**45); // RAD: 45 decimals
+    ```
+3. Set collateral debt ceiling `line` (with lower `l`)
+    ```solidity
+    vat.file('CENT-A', 'line', 1_000_000 * 10**45); // RAD: 45 decimals
+    ```
+4. Set collateral price (`spot`)
+    ```solidity
+    vat.file('CENT-A', 'spot', 1 * 10**27) // RAY: 27 decimals 
+    ```
+    - This makes so 1 `$CENT` = 1 `DAI` and that the collateralization ratio is 100%
+
+## Borrow `$MYDAI` from `$CENT`
+
+1. Approve `GemJoin` to spend your `$CENT`
+    ```solidity
+    cent.approve(<gem_join_addr>, type(uint256).max);
+    ```
+2. Add your `$CENT` to the protocol by calling `GemJoin.join()`:
+    ```solidity
+    gemJoin.join(<your_addr>, <amount>); // <amount> with 10**18 precision
+    ```
+    - This will add collateral to the system, but it will remain **unemcumbered** (not locked).
+3. Draw internal `dai` from the `Vat` using `frob()`:
+    ```solidity
+    vat.frob(
+        'CENT-A', // ilk
+        <your_wallet>,
+        <your_wallet>,
+        <your_wallet>, // To keep it simple, use your address for both `u`, `v` and `w`
+        int dink, // with 10**18 precision
+        int dart // with 10**18 precision
+    )
+    ```
+    - `dink`: how much collateral to lock(+)/unlock(-)
+        - Collateral is now **encumbered** (locked) into the system.
+    - `dart`: how much **normalized debt** to add(+)/remove(-)
+        - Remember that `debt = ilk.rate * urn.art`
+        - To get the value for `dart`, divide the desired amount by `ilk.rate` (this is a floating point division, which can be tricky)
+            - See the [RwaUrn](https://github.com/makerdao/rwa-toolkit/blob/8d30ed2cb657641253d45b57c894613e26b4ae1b/src/urns/RwaUrn.sol#L156-L178) component to understand how it can be done
+    - Recommendation: respect `dink = dart/2` when drawing
+4. Get ERC-20 `$MYDAI`
+    ```solidity
+    daiJoin.exit(<your_wallet>, <amount>); // <amount> with 10**18 precision
+    ```
+
+## Repay your loan to get `$CENT` back
+
+1. Approve `DaiJoin` to spend your `$MYDAI`
+    ```solidity
+    dai.approve(<dai_join_addr>, type(uint256).max);
+    ```
+2. Add your `$MYDAI` to the protocol by calling `DaiJoin.join()`:
+    ```solidity
+    daiJoin.join(<your_addr>, <amount>); // <amount> with 10**18 precision
+    ```
+    - This will burn ERC-20 `$MYDAI` and add it to `<your_addr>` internal balance on the `Vat`.
+3. Repay internal `dai` in the `Vat` using `frob()`:
+    ```solidity
+    vat.frob(
+        'CENT-A', // ilk
+        <your_wallet>,
+        <your_wallet>,
+        <your_wallet>, // To keep it simple, use your address for both `u`, `v` and `w`
+        int dink, // with 10**18 precision
+        int dart // with 10**18 precision
+    )
+    ```
+    - `dink`: how much collateral to unlock. **MUST BE NEGATIVE**
+        - Collateral is now **uncumbered** (unlocked), but still in the system.
+    - `dart`: how much **normalized debt** to remove. **MUST BE NEGATIVE**
+        - Remember that `debt = ilk.rate * urn.art`
+        - To get the value for `dart`, divide the desired amount by `ilk.rate` (this is a floating point division, which can be tricky)
+            - See the [RwaUrn](https://github.com/makerdao/rwa-toolkit/blob/8d30ed2cb657641253d45b57c894613e26b4ae1b/src/urns/RwaUrn.sol#L156-L178) component to understand how it can be done
+4. Get your `$CENT` back:
+    ```solidity
+    gemJoin.exit(<your_wallet>, <amount>); // <amount> with 10**18 precision
+    ```