fix: Recreate JSON-RPC request in MultichainRouter (#3086)

Recreate the JSON-RPC request in MultichainRouter to remove any
unnecesary properties passed in from the middlewares in the client. This
ensures that we don't leak unnecessary details to Snaps and also makes
sure the requests are formatted as expected downstream.

Author: FrederikBolding

packages/snaps-controllers/coverage.json

@@ -1,5 +1,5 @@
 {
-  "branches": 93.28,
+  "branches": 93.31,
   "functions": 96.8,
   "lines": 98.15,
   "statements": 97.88

packages/snaps-controllers/src/multichain/MultichainRouter.ts

@@ -18,6 +18,7 @@ import {
   KnownCaipNamespace,
   parseCaipAccountId,
 } from '@metamask/utils';
+import { nanoid } from 'nanoid';
 
 import { getRunnableSnaps } from '../snaps';
 import type { GetAllSnaps, HandleSnapRequest } from '../snaps';
@@ -291,7 +292,7 @@ export class MultichainRouter {
     connectedAddresses,
     origin,
     scope,
-    request,
+    request: rawRequest,
   }: {
     connectedAddresses: CaipAccountId[];
     origin: string;
@@ -304,6 +305,14 @@ export class MultichainRouter {
         !scope.startsWith('wallet:eip155'),
     );
 
+    // Re-create the request to simplify and remove additional properties that may be present in MM middleware.
+    const request = {
+      jsonrpc: '2.0' as const,
+      id: rawRequest.id ?? nanoid(),
+      method: rawRequest.method,
+      params: rawRequest.params,
+    };
+
     const { method, params } = request;
 
     // If the RPC request can be serviced by an account Snap, route it there.