[data-providers] - document the SubresourceDataProviderInterface usage

[gorghoa]

Document the SubresourceDataProviderInterface in custom context.

[gorghoa]

I think this is a @soyuka based feature, if you could review me, I’ll promise next time you’ll come to Amiens, weather will be sunny :sun_with_face:

[dunglas]

@gorghoa great improvement, do you think you can finish this one?

[floxblah]

Hello i found about this SubresourceDataProviderInterface randomly and this kind of make me succeed to implement a custom path to get all the subressource of an entity (see my post on stack overflow for more details)

Is this interface "usable" and supported by api platform ? is it or will it be deprecated in a future release?

[soyuka]

Is this interface "usable" and supported by api platform ? is it or will it be deprecated in a future release?

It'll be deprecated in 2.7 and removed in 3.0.