Proposal to TM Forum (Apache 2.0) Network Slice Management API

A fully working E2E Network Slicing REST API with Swagger, Postman collection and HTML Documentation (AP-1284). Includes Slice Catalog operations with GSMA GST implementation. The team defined a concrete API for slice management that deals with the needs of the users of the API (slice tenants). The design of API specification blends the data model work 3GPP SA5, the aforementioned GST JSON template, TM Forum API Restful Guidelines into a cohesive endpoint for use of the TM Forum and to progress the industries understanding of how different SDO concepts relate to each other. The API defined gives a balanced focus on the entire set of lifecycle operations rather than simply focus on slice creation. On slice creation, the 3-step process of allocating, configuring and activating slices of the network is evangelized. Overall we believe create slice operations will be infrequent in practice; most daily operations will be focused on allocating new service orders to existing slices. https://projects.tmforum.org/jira/browse/AP-1284