Add storage description link discovery

[SarthakDudhe]

Add storageDescription Link headers for GET, HEAD, and OPTIONS requests.
Point the relation to the root storage metadata resource (/.meta).
Cover resources and containers in HTTP integration tests.

Fixes #1805.

Tests

npm run lint
npm run mocha-integration

[csarven]

Great, thanks for doing this. I haven't run the tests but this generally looks good to me. I've run the code locally and it is referring to the expected URL for storage description resource.

Does this code assume that storage root is always at req.hostname + '/'?

I can't remember now but does NSS allow non-root path to be storage root? If so, does the code take that into account?

[bourgeoa]

I can't remember now but does NSS allow non-root path to be storage root? If so, does the code take that into account?

NSS only allow subdomain. Storage starts at root path.

[csarven]

Ok, great. If you review / approve, we should merge this.

[bourgeoa]

@csarven @SarthakDudhe

From https://solidproject.org/TR/protocol#storage-description-statements
I think that root/.meta must include the triple

</> a <http://www.w3.org/ns/pim/space#Storage> .

Which is not actually the case.

If this is correct it implies to

• update default root/.meta
• prepare a migration script for existing servers

[csarven]

In NSS, it'd be (the slash for the storage resource):

</> a <http://www.w3.org/ns/pim/space#Storage> .

I don't understand why a migration script is necessary (although I understand it'd be useful to do).

[bourgeoa]

Thanks yes you are right I have updated above.
Why a migration ? This is because the triple is created at pod creation. On existing server you need to update all existing pods.
We add the same issue when Solid spec introduced pim:storage or solid:oidcIssuer in profile/card