feat: always add URI to SIWE payload (#5172)

## Problem solved

Short description of the bug fixed or feature added

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---

## PR-Codex overview
This PR focuses on ensuring that a URI is always included in the SIWE payload by modifying the logic in the `generate-login-payload.ts` file and updating the corresponding test.

### Detailed summary
- In `generate-login-payload.ts`, the `uri` field is updated to default to `options.domain` if `options.login?.uri` is not provided.
- In `generate-login-payload.test.ts`, the test case for `uri` is changed to use `"example.com"` instead of `undefined`.

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Author: joaquim-verges

.changeset/soft-weeks-know.md

@@ -0,0 +1,5 @@
+---
+"thirdweb": patch
+---
+
+Always add URI to SIWE payload

packages/thirdweb/src/auth/core/generate-login-payload.test.ts

@@ -89,7 +89,7 @@ describe("generateLoginPayload", () => {
         "issued_at": "1970-01-01T00:00:00.000Z",
         "resources": undefined,
         "statement": "Please ensure that the domain above matches the URL of the current website.",
-        "uri": undefined,
+        "uri": "example.com",
         "version": "1",
       }
     `);

packages/thirdweb/src/auth/core/generate-login-payload.ts

@@ -46,7 +46,7 @@ export function generateLoginPayload(options: AuthOptions) {
       statement: options.login?.statement || DEFAULT_LOGIN_STATEMENT,
       version: options.login?.version || DEFAULT_LOGIN_VERSION,
       resources: options.login?.resources,
-      uri: options.login?.uri,
+      uri: options.login?.uri || options.domain,
     };
   };
 }