Add functionality for key-based authentication #5
Description
Most APIs use keys to limit requests to only those authorized to use the endpoint in question. The Velox API should also allow developers to implement the same.
Because the Velox API operates as a liaison and not as a backend itself, the specific means of implementation must be left to the developer, but there should be a hook by which Velox can relay authentication details to a backend and determine based on the response whether the requester is authorized to query the endpoint in question.