feat: add organization parameter support to token exchange

[yogeshchoudhary147]

Description

Adds support for the organization parameter in the token exchange flow (exchangeToken method) to enable organization-specific authentication.

Changes

• Added organization as an optional parameter to CustomTokenExchangeOptions interface
• Updated exchangeToken method to conditionally pass organization to the /oauth/token endpoint
• Updated JSDoc documentation with organization parameter details and usage example
• Added test coverage for organization parameter (both provided and not provided scenarios)

API Changes

The /oauth/token endpoint now accepts an optional organization parameter for the token exchange grant type. When provided, the organization ID will be present in the access token payload.

Testing

• ✅ Added test: passes organization parameter to _requestToken when provided
• ✅ Added test: does not pass organization parameter when not provided
• ✅ All existing tests pass

Example Usage

const tokenResponse = await auth0Client.exchangeToken({
  subject_token: 'external_token',
  subject_token_type: 'urn:acme:legacy-system-token',
  scope: 'openid profile',
  organization: 'org_12345'
});
// Organization ID will be in access token payload