Spec: BBS: Broadband Services Orchestration use case

### Name: BBS: Broadband Services Orchestration use case

Description: (from https://onseu19.sched.com/event/SYuy)
BBS aims at enabling ONAP for the design, provisioning, life-cycle management, and assurance of broadband services, such as multi-Gigabit Internet Connectivity services based on PON (Passive Optical Network) access technology. The use case covers new scenarios, such as nomadic ONT (Optical Network Terminal) and service subscription plan changes.

BBS use case shows the extensibility of the ONAP platform in supporting the orchestration of services across different locations (e.g., Central Office, Core) and technology domains (e.g., Access, Edge).

We'd like to add the BBS Use Case to the CNF Testbed in the near future.

References:

- [ ] https://static.sched.com/hosted_files/onseu19/76/20190925_ONS_ONAP_BBS_Broadband_Service_final_.pdf

- [ ] [ONAP wiki page for BBS use case](https://wiki.onap.org/pages/viewpage.action?pageId=45297636)

- [ ] https://wiki.onap.org/display/DW/BBS+Modeling

- [ ] https://github.com/onap/doc/blob/master/docs/guides/onap-developer/architecture/onap-architecture.rst#broadband-service-bbs