Add optional custom request queue assignment to Requestables. Custom queues will be an optional implementation allowing the host application to define custom request queues.

Use case

Low priority, background requests could be directed to a specified queue to avoid "clogging" the request pipeline for more critical requests. For example, having all authentication/token refresh requests run on a dedicated queue would prevent them from fighting against other priority requests.

Goals

• Queues should allow for custom configurations, for example, the label and the maximum number of requests.
• The queue definition should be static as part of the Requestable protocol. The library would create and manage the queues as needed.
• Jumping queues would be useful given the library merges requests and currently raises/lowers request priority based on observers. However, this could be challenging if queues are defined statically on requests. The queue definition might need to allow for a more conditional definition. An initial thought could be a structure defining multiple queues with jump rules. Ideally, this would all be optional and thus only introduce complexity for those who need it.

Add a Retryable protocol to go along with Requestable and Cacheable that defines requests that should be retried on failure. The protocol should allow for defining the retry policy.

This networking package is called "DeclarativeNetworking"; that just won't do!

The order in which query params are appended to the url would ideally be sorted deterministically by name.

Add the ability to expire cached data without deleting it. Applications can use this to set an endpoint data as expired when an action was taken that you know, or expect, will invalidate or update the data, but you don't need to fetch the updates immediately.

Right now, the cache layer is leveraging Cache; it's unknown if this is a supported feature of the package. One of the longer-term goals is to move to a custom caching system for more control. Ideally, that will not be needed for this feature.

Set up a protocol for defining pagination handling.