This change allows using an access token for the token exchange grant when requesting a federated connection access token. This is accomplished by adding a new subject_token_type option.

• All new/changed/fixed functionality is covered by tests (or N/A)
• I have added documentation for all new/changed functionality (or N/A)

📋 Changes

This change introduces a subject_token_type option to the getAccessTokenForConnection method. This provides the flexibility to use an access_token for the token exchange, in addition to the existing refresh_token method. The default behavior is preserved.

Usage:

// New method using an access token
await authClient.getAccessTokenForConnection(session, {
  connection: 'my-connection',
  subject_token_type: SUBJECT_TOKEN_TYPES.SUBJECT_TYPE_ACCESS_TOKEN
});

// Default method using a refresh token
await authClient.getAccessTokenForConnection(session, {
  connection: 'my-connection'
});

• Changed src/server/auth-client.ts: Use the new subject_token_type from options, defaulting to a refresh token if not provided.
• Changed src/types/index.ts: Added SUBJECT_TOKEN_TYPES enum and exposed subject_token_type in AccessTokenForConnectionOptions.

📎 References

• RFC 8693: OAuth 2.0 Token Exchange

🎯 Testing

Manual:

1. Call getAccessTokenForConnection without the new subject_token_type option.
2. Verify the call succeeds and uses the refresh_token grant type.
3. Call getAccessTokenForConnection with subject_token_type set to SUBJECT_TOKEN_TYPES.SUBJECT_TYPE_ACCESS_TOKEN.
4. Verify the call succeeds and uses the access_token grant type.