LinkedIn OAuth2 Client ID. Get from LinkedIn Developer Portal: 1) Go to developer.linkedin.com and sign in. 2) Click "Create App". 3) Fill app details (name, company, description). 4) After creation, find your Client ID on the Auth tab. For detailed documentation, see: https://learn.microsoft.com/en-us/linkedin/shared/authentication/authentication#application-authorization-2-legged-oauth-client-credential-flow
