Create a cached ITerminologyService

[ewoutkramer]

Create a TermServiceCacher implementation of ITerminologyService (or at least for the interface that includes codesystem-validate-code and valueset-validate-code) and let it cache the calls to a terminology service. If a certain number of hits per minute for a valueset has been reached, ask for the expansion and then answer locally. Note that this requires care: we should make sure the local semantics for the check are the same as the external semantics. In any doubt (e.g. parameters that we don't understand) => refer back to the original terminology service.