Add ERC6909 Implementation along with extensions (#5394)

Co-authored-by: Hadrien Croubois <hadrien.croubois@gmail.com>
Co-authored-by: Ernesto García <ernestognw@gmail.com>

test/token/ERC6909/extensions/ERC6909TokenSupply.test.js

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+const { ethers } = require('hardhat');
+const { expect } = require('chai');
+const { loadFixture } = require('@nomicfoundation/hardhat-network-helpers');
+
+const { shouldBehaveLikeERC6909 } = require('../ERC6909.behavior');
+
+async function fixture() {
+  const [holder, operator, recipient, other] = await ethers.getSigners();
+  const token = await ethers.deployContract('$ERC6909TokenSupply');
+  return { token, holder, operator, recipient, other };
+}
+
+describe('ERC6909TokenSupply', function () {
+  beforeEach(async function () {
+    Object.assign(this, await loadFixture(fixture));
+  });
+
+  shouldBehaveLikeERC6909();
+
+  describe('totalSupply', function () {
+    it('is zero before any mint', async function () {
+      await expect(this.token.totalSupply(1n)).to.eventually.be.equal(0n);
+    });
+
+    it('minting tokens increases the total supply', async function () {
+      await this.token.$_mint(this.holder, 1n, 17n);
+      await expect(this.token.totalSupply(1n)).to.eventually.be.equal(17n);
+    });
+
+    describe('with tokens minted', function () {
+      const supply = 1000n;
+
+      beforeEach(async function () {
+        await this.token.$_mint(this.holder, 1n, supply);
+      });
+
+      it('burning tokens decreases the total supply', async function () {
+        await this.token.$_burn(this.holder, 1n, 17n);
+        await expect(this.token.totalSupply(1n)).to.eventually.be.equal(supply - 17n);
+      });
+
+      it('supply unaffected by transfers', async function () {
+        await this.token.$_transfer(this.holder, this.recipient, 1n, 42n);
+        await expect(this.token.totalSupply(1n)).to.eventually.be.equal(supply);
+      });
+
+      it('supply unaffected by no-op', async function () {
+        await this.token.$_update(ethers.ZeroAddress, ethers.ZeroAddress, 1n, 42n);
+        await expect(this.token.totalSupply(1n)).to.eventually.be.equal(supply);
+      });
+    });
+  });
+});