Rewrite the W3C API on top of Symfony API Platform

[vivienlacourba]

Symfony's API Platform is a REST and GraphQL framework to build modern API-driven projects.

We should rewrite the W3C API based on this framework (which did not existed when we developed the initial version of the W3C API).

This will provide long requested features such as:

• Filtering (see Allow to filter results #76, Add filters to retrieve only W3C Member organizations #41, Way to retrieve list of closed groups #68 )
• Default order (see Sort lists of items sensibly before returning them (?) #71) and Sorting
• Improved performances (built-in HTTP Cache Invalidation System) (see Provide Last-Modified headers on more routes #60)
• Additional output formats (JSON-LD) (See RDF (Turtle) output  #38)
• GraphQL
• and many other API Platform features.