Exchange a refresh token for an updated access token.
Supports multiple client authentication methods as specified in OAuth 2.1:
The authorization server's base URL
Configuration object containing client info, refresh token, etc.
Promise resolving to OAuth tokens (preserves original refresh_token if not replaced)
refresh_token
When token refresh fails or authentication is invalid
Exchange a refresh token for an updated access token.
Supports multiple client authentication methods as specified in OAuth 2.1: