Revert "remove clients"

This reverts commit 7443666.

# Conflicts:
#	package.json
#	tsconfig.json

clients/config/overrides.ts

@@ -0,0 +1,8 @@
+import { CallOverrides } from "@ethersproject/contracts";
+
+// https://docs.immutable.com/docs/zkEVM/architecture/gas-config
+export const defaultGasOverrides: CallOverrides = {
+  maxPriorityFeePerGas: 10e9, // 10 Gwei
+  maxFeePerGas: 15e9,
+  gasLimit: 200000, // Expected when setting the above properties
+};

clients/erc20.ts

@@ -0,0 +1,82 @@
+import { Overrides } from "ethers";
+import { Provider } from "@ethersproject/providers";
+import { BigNumberish, BigNumber } from "@ethersproject/bignumber";
+import { CallOverrides, PopulatedTransaction } from "@ethersproject/contracts";
+
+import { ERC20 } from "../typechain-types/@openzeppelin/contracts/token/ERC20";
+import { ERC20__factory } from "../typechain-types/factories/@openzeppelin/contracts/token/ERC20/ERC20__factory";
+import { PromiseOrValue } from "../typechain-types/common";
+import { defaultGasOverrides } from "./config/overrides";
+
+export class ERC20Client {
+  private readonly contract: ERC20;
+
+  constructor(contractAddress: string) {
+    const factory = new ERC20__factory();
+    this.contract = factory.attach(contractAddress);
+  }
+
+  /**
+   * @returns a promise that resolves with a BigNumber that represents the amount of tokens in existence
+   */
+  public async totalSupply(provider: Provider, overrides: CallOverrides = {}): Promise<BigNumber> {
+    return this.contract.connect(provider).totalSupply(overrides);
+  }
+
+  /**
+   * @returns a promise that resolves with a BigNumber that represents the amount of tokens owned by account
+   */
+  public async balanceOf(
+    provider: Provider,
+    account: PromiseOrValue<string>,
+    overrides: CallOverrides = {},
+  ): Promise<BigNumber> {
+    return this.contract.connect(provider).balanceOf(account, overrides);
+  }
+
+  /**
+   * @returns a promise that resolves with a BigNumber that represents the remaining number of tokens that spender will be allowed to spend on behalf of owner through transferFrom
+   */
+  public async allowance(
+    provider: Provider,
+    owner: PromiseOrValue<string>,
+    spender: PromiseOrValue<string>,
+    overrides: CallOverrides = {},
+  ): Promise<BigNumber> {
+    return this.contract.connect(provider).allowance(owner, spender, overrides);
+  }
+
+  /**
+   * @returns a promise that resolves with a populated transaction
+   */
+  public async populateTransfer(
+    to: PromiseOrValue<string>,
+    amount: PromiseOrValue<BigNumberish>,
+    overrides: Overrides & { from?: PromiseOrValue<string> } = {},
+  ): Promise<PopulatedTransaction> {
+    return this.contract.populateTransaction.transfer(to, amount, { ...defaultGasOverrides, ...overrides });
+  }
+
+  /**
+   * @returns a promise that resolves with a populated transaction
+   */
+  public async populateApprove(
+    spender: PromiseOrValue<string>,
+    amount: PromiseOrValue<BigNumberish>,
+    overrides: Overrides & { from?: PromiseOrValue<string> } = {},
+  ): Promise<PopulatedTransaction> {
+    return this.contract.populateTransaction.approve(spender, amount, { ...defaultGasOverrides, ...overrides });
+  }
+
+  /**
+   * @returns a promise that resolves with a populated transaction
+   */
+  public async populateTransferFrom(
+    from: PromiseOrValue<string>,
+    to: PromiseOrValue<string>,
+    amount: PromiseOrValue<BigNumberish>,
+    overrides: Overrides & { from?: PromiseOrValue<string> } = {},
+  ): Promise<PopulatedTransaction> {
+    return this.contract.populateTransaction.transferFrom(from, to, amount, { ...defaultGasOverrides, ...overrides });
+  }
+}