Hi,

Hope you gone through below information which is present in above link.

If you create REST Service using Pega, you can use Authentication Type in service package data instance. There you have an option to select the type of authentication. You can select "Custom" as authentication type for Container managed systems.

• Authentication type - Select the type of authentication to use. Select Basic authentication for HTTP-based services such as REST, HTTP, SOAP, and SAP. Select custom authentication to select an authentication service. When you select Custom, the Authentication service field is displayed for selecting the authentication service to use.
• Authentication service - This field appears only when Requires authentication ? is checked and Authentication type is Custom. If you are using LDAP authentication, select an authentication service (a Data-Admin-AuthService instance) when the service type is SOAP (Rule-Service-SOAP) or HTTP (Rule-Service-HTTP), SAP (Rule-Service-SAP, or REST (Rule-Service-REST).

  Note:Authentication service is required only for custom authentication including LDAP and SAML 2.0 authentication. You could also use HTTP Basic for user authentication, or, in the case of HTTP Service you could provide the HTTP headers UserIdentifier and Password for user authentication instead of basic authentication.

Kindly refer https://community.pega.com/sites/default/files/help_v721/procomhelpmain.htm