Get custom fields from contracts

## Authentication Deel API uses API tokens to authenticate requests. A bearer token is required to authenticate all API requests. All API requests must be made over HTTPS. Calls made over plain HTTP will fail. API requests without authentication will also fail. ``` curl -X GET 'api.letsdeel.com/rest/v2/contracts' \ -H 'Authorization: Bearer YOUR-TOKEN-HERE' ``` ### Generating Access Tokens 1. Navigate to **Apps & Perks > Developer Center**. 2. Click on the “Generate New Token” button. 3. In the popup, click “Generate Token” button to generate a new token. Your newly generated token is visible on the screen. 4. Make sure to copy and save your token once is generated. You won't be able to see it again!

Standard OAuth2 security scheme based on https://swagger.io/docs/specification/authentication/