Consider storing the DEP-synced devices

[jessepeterson]

This feature was deliberately left out of NanoDEP as "out of scope."

Reasons for NOT including this feature: (i.e. the way it is now):

• Not technically required for the MVP of auto-assigning DEP profiles to serials.
• We already export webhook functionality which one can implement this feature oneself.
  • Similarly the internal godep API is structured in such a way as to implement this oneself.

Reasons to change course and include this feature:

• This may just be an "expected" feature.
• It could help dealing with the "Reassignment Oddities" for auto-assignment by having more information about a given serial number.
• It would be relatively simple to implement — mostly just UPSERT operations on the sync/fetches — and then a query API/interface (which of course would need to be storage backend agnostic).