feat: function to create self-delegated app-side signers

This means, they already include the self-delegation authorization from the encryptor

packages/taco-auth/src/providers/encryptor/self-delegate.ts

@@ -1,4 +1,4 @@
-import { ethers } from 'ethers';
+import { Wallet, ethers } from 'ethers';
 import { z } from 'zod';
 
 import { AuthSignature } from '../../auth-sig';
@@ -15,6 +15,15 @@ export class SelfDelegateProvider {
     this.storage = new LocalStorage();
   }
 
+  public async createSelfDelegatedAppSideSigner(
+    ephemeralPrivateKey: any  // TODO: Find a stricter type
+  ): Promise<[ethers.Signer, AuthSignature]> {
+    const appSideSigner = new Wallet(ephemeralPrivateKey);
+    const appSideSignerAddress = await appSideSigner.getAddress();
+    const authSignature = await this.getOrCreateAuthSignature(appSideSignerAddress);
+    return [appSideSigner, authSignature];
+  }
+
   public async getOrCreateAuthSignature(
     ephemeralPublicKeyOrAddress: string
   ): Promise<AuthSignature> {

packages/taco-auth/test/auth-provider.test.ts

@@ -140,11 +140,18 @@ describe('encryptor self-delegate provider authorization', () => {
   const provider = fakeProvider(bobSecretKeyBytes);
   const signer = provider.getSigner();
   const selfDelegateProvider = new SelfDelegateProvider(signer);
+
+  it('creates a new self-delegated app signer', async () => {
+    const appSideSignerAddress = await applicationSideSigner.getAddress();
+    const [newSigner, newAuthSignature] = await selfDelegateProvider.createSelfDelegatedAppSideSigner(aliceSecretKeyBytes);
+    expect(await newSigner.getAddress()).toEqual(appSideSignerAddress);
+    expect(newAuthSignature.typedData).toEqual(appSideSignerAddress);
+  });
 
   const applicationSideProvider = fakeProvider(aliceSecretKeyBytes);
   const applicationSideSigner = applicationSideProvider.getSigner();
 
-  it('creates a new  message', async () => {
+  it('creates a new auth signature', async () => {
     const appSideSignerAddress = await applicationSideSigner.getAddress();
     const typedSignature = await selfDelegateProvider.getOrCreateAuthSignature(appSideSignerAddress);
     expect(typedSignature.signature).toBeDefined();