feat(auth): expose siwe message creator to user-facing api

packages/taco-auth/src/eip4361.ts

@@ -34,10 +34,17 @@ export class EIP4361SignatureProvider {
 
   private async createSiweMessage(): Promise<AuthSignature> {
     const address = await this.signer.getAddress();
+    const chainId = (await this.provider.getNetwork()).chainId;
     const { domain, uri } = this.getParametersOrDefault();
+    const message = EIP4361SignatureProvider.prepareSiweMessage(address, chainId, domain, uri);
+    const signature = await this.signer.signMessage(message);
+    const scheme = 'EIP4361';
+    return { signature, address, scheme, typedData: message };
+  }
+
+  public static prepareSiweMessage(address: string, chainId: number, domain: string, uri: string) {
     const version = '1';
     const nonce = generateNonce();
-    const chainId = (await this.provider.getNetwork()).chainId;
     const siweMessage = new SiweMessage({
       domain,
       address,
@@ -47,10 +54,7 @@ export class EIP4361SignatureProvider {
       nonce,
       chainId,
     });
-    const scheme = 'EIP4361';
-    const message = siweMessage.prepareMessage();
-    const signature = await this.signer.signMessage(message);
-    return { signature, address, scheme, typedData: message };
+    return siweMessage.prepareMessage();
   }
 
   private getParametersOrDefault() {