Refreshes the cached bot identity for this configuration.

Calls the per-provider `IBotIdentityResolver` (Telegram `getMe`, Slack `auth.test`) and persists the resolved handle / display name / provider id onto the config. Drives the participant dialog's empty-state hint ("Send a message to @your_bot to populate suggestions"). Returns 200 with the resolved identity when the resolver could talk to the provider, 200 with the previously stored identity (or null) when credentials aren't connected yet — never 500 for a steady-state miss. Integrations without a resolver (Teams, Twilio, Dialog360 today) return 200 with null.

curl -X POST "https://api.fruxon.com/v1/tenants/string/integrations/string/configs/497f6eca-6276-4993-bfeb-53cbbbba6f08:refreshIdentity"

{
  "handle": "string",
  "displayName": "string",
  "providerId": "string",
  "fetchedAt": 0
}

{
  "type": "string",
  "title": "string",
  "status": 0,
  "detail": "string",
  "instance": "string",
  "property1": null,
  "property2": null
}