api: Allow nested map[string]interface{} template data

* Support templating lists into Ignition (e.g. SSH authorized keys)

api/cloud.go

@@ -36,7 +36,7 @@ func cloudHandler(store Store) ContextHandler {
 		}
 
 		// collect data for rendering
-		data := make(map[string]string)
+		data := make(map[string]interface{})
 		for k := range group.Metadata {
 			data[k] = group.Metadata[k]
 		}

api/groups.go

@@ -20,7 +20,7 @@ type Group struct {
 	// Spec identifier
 	Spec string `yaml:"spec"`
 	// Custom Metadata
-	Metadata map[string]string `yaml:"metadata"`
+	Metadata map[string]interface{} `yaml:"metadata"`
 	// matcher conditions
 	Matcher RequirementSet `yaml:"require"`
 }

api/groups_test.go

@@ -17,7 +17,7 @@ var (
 	testGroup           = Group{
 		Name: "test group",
 		Spec: "g1h2i3j4",
-		Metadata: map[string]string{
+		Metadata: map[string]interface{}{
 			"k8s_version":  "v1.1.2",
 			"pod_network":  "10.2.0.0/16",
 			"service_name": "etcd2",

api/ignition.go

@@ -33,7 +33,7 @@ func ignitionHandler(store Store) ContextHandler {
 		}
 
 		// collect data for rendering Ignition Config
-		data := make(map[string]string)
+		data := make(map[string]interface{})
 		for k := range group.Metadata {
 			data[k] = group.Metadata[k]
 		}