add interface for getting configurations

Signed-off-by: nirvanagit <[email protected]>

admiral/pkg/registry/registry.go

@@ -0,0 +1,10 @@
+package registry
+
+// IdentityConfiguration is an interface to fetch configuration from a registry
+// backend. The backend can provide an API to give configurations per identity,
+// or if given a cluster name, it will provide the configurations for all
+// the identities present in that cluster.
+type IdentityConfiguration interface {
+	GetByIdentity(identityAlias string) error
+	GetByCluster(clusterName string) error
+}