DynamicHTTPMetadataProvider fetches entity metadata just-in-time from a remote HTTP server. The metadata request URL is constructed by applying a transform to the
entityID. The transform strategy is configured in a child element.
Metadata is cached in memory subject to a complex set of interacting settings and the cache indicators within the metadata itself, and also can be saved to disk and reloaded back into memory at reload or startup time to restore the state of the cache. This isn't a fully redundant safety net but can be used as part of an overall strategy to reduce the risk of relying on remote sources in real-time. Ultimately, remote sources have to be bulletproof or there will be outages. This can be mitigated but not fully eliminated as a risk.