Require hook maturity level on hook definition

Fixes #444

Author: isaacvetter

docs/specification/1.0.md

@@ -873,7 +873,9 @@ Hook creators SHOULD include examples of the context.
 If the context contains FHIR data, hook creators SHOULD include examples across multiple versions of FHIR if differences across FHIR versions are possible.
 
 ### Hook Maturity Model
-The intent of the CDS Hooks Maturity Model is to attain broad community engagement and consensus, before a hook is labeled as mature, that the hook is necessary, implementable, and worthwhile to the CDS services and CDS clients that would reasonably be expected to use it. Implementer feedback should drive the maturity of new hooks. Diverse participation in open developer forums and events, such as HL7 FHIR Connectathons, is necessary to achieve significant implementer feedback. The below criteria will be evaluated with these goals in mind.
+The intent of the CDS Hooks Maturity Model is to attain broad community engagement and consensus, before a hook is labeled as mature, that the hook is necessary, implementable, and worthwhile to the CDS services and CDS clients that would reasonably be expected to use it. Implementer feedback should drive the maturity of new hooks. Diverse participation in open developer forums and events, such as HL7 FHIR Connectathons, is necessary to achieve significant implementer feedback. The below criteria will be evaluated with these goals in mind. The hook definition defines the hook's current maturity level and MUST link to the definition of that maturity level.
+
+    Hook maturity | 3 - Considered
 
 The Hook maturity levels use the term CDS client to generically refer to the clinical workflow system in which a CDS services returned cards are displayed.