(a) Except as otherwise provided in subdivision (b), a contract to render personal service, other than a contract of apprenticeship as provided in Chapter 4 (commencing with Section 3070), may not be enforced against the employee beyond seven years from the commencement of service under it. Any contract, otherwise valid, to perform or render service of a special, unique, unusual, extraordinary, or intellectual character, which gives it peculiar value and the loss of which cannot be reasonably or