Creates a new contact for a customer or site.

• firstName is required
• email is optional and must be a valid email address when provided. This will be added as a contact item.
• At least one contact item is required: provide email and/or at least one entry in contactItems.
• contactType is required and must be one of the following: CUSTOMER, SITE.
  • When contactType is CUSTOMER:
    • customerId is required
    • isMain cannot be set to true and is optional. To update the main contact, use the '/customers' endpoint.
    • isBilling is optional and defaults to false.
  • When contactType is SITE:
    • siteId is required
    • isMain is optional and defaults to false.
    • isBilling is optional and defaults to false.