Bixby Developer Center

Specifies the name of the secrets key, set in the Configuration & Secrets screen of the Bixby Developer Center, which stores the OAuth client secret.

authorization {
  user {
    oauth2-authorization-code (providerId) {
      authorize-endpoint (...)
      client-id (...)
      client-secret-key (...)
      scope (...)  // optional
      token-endpoint (...)
    }
  }
  global {
    oauth2-client-credentials (providerId) {
      client-id (...)
      client-secret-key (...)
      scope (...)  // optional
      token-endpoint (...)
    }
  }
}

The client-secret-key is a name entered in the Configuration & Secrets screen of the Bixby Developer Center for the capsule:

To get the secret with the name sec1, your authorization block would contain client-secret-key (sec1).