Added work_email read and write for contractors

We've added work_email to contractor endpoints for both read and write, bringing contractors to parity with employees on work email.

Use work_email to read a contractor's work email with Get a contractor, and set it with Update a contractor. Contractors previously exposed only the personal or sign-up email field, so you can now manage work email consistently across employees and contractors.

This field is additive and doesn't change the existing contractor response shape. Returns null when unset, matching employee behavior.

Read more in our Manage contractors guide.