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/ERC6909ContentURI.test.js

@@ -0,0 +1,49 @@
+const { ethers } = require('hardhat');
+const { expect } = require('chai');
+const { loadFixture } = require('@nomicfoundation/hardhat-network-helpers');
+
+async function fixture() {
+  const token = await ethers.deployContract('$ERC6909ContentURI');
+  return { token };
+}
+
+describe('ERC6909ContentURI', function () {
+  beforeEach(async function () {
+    Object.assign(this, await loadFixture(fixture));
+  });
+
+  describe('contractURI', function () {
+    it('is empty string be default', async function () {
+      await expect(this.token.contractURI()).to.eventually.equal('');
+    });
+
+    it('is settable by internal setter', async function () {
+      await this.token.$_setContractURI('https://example.com');
+      await expect(this.token.contractURI()).to.eventually.equal('https://example.com');
+    });
+
+    it('emits an event when set', async function () {
+      await expect(this.token.$_setContractURI('https://example.com')).to.emit(this.token, 'ContractURIUpdated');
+    });
+  });
+
+  describe('tokenURI', function () {
+    it('is empty string be default', async function () {
+      await expect(this.token.tokenURI(1n)).to.eventually.equal('');
+    });
+
+    it('can be set by dedicated setter', async function () {
+      await this.token.$_setTokenURI(1n, 'https://example.com/1');
+      await expect(this.token.tokenURI(1n)).to.eventually.equal('https://example.com/1');
+
+      // Only set for the specified token ID
+      await expect(this.token.tokenURI(2n)).to.eventually.equal('');
+    });
+
+    it('emits an event when set', async function () {
+      await expect(this.token.$_setTokenURI(1n, 'https://example.com/1'))
+        .to.emit(this.token, 'URI')
+        .withArgs('https://example.com/1', 1n);
+    });
+  });
+});