Add erc2477 interface.

packages/0xcert-ethereum-xcert-contracts/src/contracts/ierc-2477.sol

@@ -4,7 +4,7 @@ pragma solidity 0.8.6;
 /**
  * @title ERC-2477 Non-Fungible Token Metadata Integrity Standard
  * @dev See https://eips.ethereum.org/EIPS/eip-2477
- * @dev The ERC-165 identifier for this interface is 0x#######. //TODO: FIX THIS
+ * @dev The ERC-165 identifier for this interface is 0x832a7e0e
  */
 interface ERC2477 /* is ERC165 */ {
   /**

packages/0xcert-ethereum-xcert-contracts/src/contracts/utils/selector.sol

@@ -2,6 +2,7 @@
 
 pragma solidity 0.8.6;
 
+import "../ierc-2477.sol";
 import "../ixcert.sol";
 import "../ixcert-burnable.sol";
 import "../ixcert-mutable.sol";
@@ -16,6 +17,18 @@ import "../ixcert-revokable.sol";
 contract Selector
 {
 
+  /**
+   * @dev Calculates and returns interface ID for the erc2477 smart contract.
+   */
+  function calculateERC2477Selector()
+    external
+    pure
+    returns (bytes4)
+  {
+    ERC2477 i;
+    return (i.tokenURIIntegrity.selector ^ i.tokenURISchemaIntegrity.selector);
+  }
+
   /**
    * @dev Calculates and returns interface ID for the Xcert smart contract.
    */

packages/0xcert-ethereum-xcert-contracts/src/contracts/xcert.sol

@@ -156,6 +156,7 @@ contract XcertToken is
   constructor()
   {
     supportedInterfaces[0x39541724] = true; // Xcert
+    supportedInterfaces[0x832a7e0e] = true; // ERC2477
   }
 
   /**

packages/0xcert-ethereum-xcert-contracts/src/tests/utils/selector.test.ts

@@ -20,6 +20,19 @@ spec.beforeEach(async (ctx) => {
   ctx.set('selector', selector);
 });
 
+spec.test('checks erc2477 selector', async (ctx) => {
+  const selector = ctx.get('selector');
+  const xcert = await ctx.deploy({
+    src: './build/xcert-mock.json',
+    contract: 'XcertMock',
+    args: ['Foo', 'F', 'https://0xcert.org/', '.json', '0x9c22ff5f21f0b81b113e63f7db6da94fedef11b2119b4088b89664fb9a3cb658', []],
+  });
+
+  const bytes = await selector.instance.methods.calculateERC2477Selector().call();
+  const supports = await xcert.instance.methods.supportsInterface(bytes).call();
+  ctx.is(supports, true);
+});
+
 spec.test('checks Xcert selector', async (ctx) => {
   const selector = ctx.get('selector');
   const xcert = await ctx.deploy({