Subscriptions to individual EndDevices can't be made via Aggregator EndDevice

[joshvote]

Trying to subscribe to a particular EndDevice's resources (eg /edev/123/derp/doe/derc) by POSTing to the aggregator EndDevice /edev/0/sub will return a HTTP 400.

The error is that the SubscriptionManager sees a mismatch between scope (edev 0) and subscribed resource (edev 123). In this particular example - IF the edev belongs to the aggregator scope, it should probably be allowed. If it's an edev outside the current aggregator's scope - the existing failure should still be returned as is.

[joshvote]

As I look more into this - I'm tempted to make this a WONT FIX but with the caveat that we need to improve the error message being returned.

Mismatch on subscribedResource EndDevice id XXXX expected None is not all that helpful

Something like subscribedResource's EndDevice (id XXXX) must match the subscription EndDevice (id 0)