Creates a Service Item

Assets (assets), this parameters describe a list of rules which a time must
satisfy to be considered available.
An Asset consists of a

• company_rule -> can be either default (it will respect the company of the URL), any (it can be any company that provides the service), or Array<CompanyID> one of these companies (which must provide the service).
• person_rule -> can be either any (any person which provides the service), any_or_none (the user is indifferent as to whether a person is associated to the booking), Array<PersonID> one of these people who provide the service.
• resource_rule -> same as person_rule: can be either any (any resource which provides the service), any_or_none (the user is indifferent as to whether a resource is associated to the booking), Array<PersonID> one of these resources with which the service can be provided.