DCAT-AP description for all created streams

[pietercolpaert]

I would love that the root of the server with multiple Sources has an overview of all sources available, listed with DCAT-AP similar to these examples:

• https://smartdata.dev-vlaanderen.be/base
• https://apidg.gent.be/opendata/adlib2eventstream/v1/

(read it as RDF triples, not as JSON)