Create a POST body content as provided in API Doc. Each contact can have following parameters:
number (mandatory), first_name, last_name, company_name, email, tag & custom.
number (mandatory)- The phone number of the contact that will be called in a campaign. It should be in E.164 format. If not set, our system will try to match it with a country and make a call. If landline number, prefix it with STD code; Ex: 0XXXXXX2400
first_name (optional) – The first name of the contact
last_name (optional) – The last name of the contact
company_name(optional) – The company name of the contact
email(optional) – The email ID of the contact
tag(optional) – The tag with which this contact will be associated with
custom(optional) – Custom field to allow you to pass any number of key value pairs in JSON format