Document best practices for implementing a remote server-based provider #130
Description
Explain the usual steps and decision points, based on ReloadingFileProvider and hypothetical RemoteServerProvider and RefetchingRemoteServerProvider. The separation between the constant one (loads from the server once, at init time) and the refetching one (fetches at init time, then reloads periodically) is important as only the latter needs to conform to Service and needs to be added to a service lifecycle service group.