support multi o365 account to choose which to auth (#2399)

ref: https://docs.microsoft.com/en-us/azure/active-directory/develop/v2-oauth2-auth-code-flow#request-an-authorization-code

app/internal_packages/onboarding/lib/onboarding-helpers.ts

@@ -322,6 +322,7 @@ export function buildO365AuthURL() {
     response_mode: 'query',
     code_challenge: CODE_CHALLENGE,
     code_challenge_method: 'S256',
+    prompt: 'select_account',
   })}`;
 }