Viewer metrics api (#208)

* Add support for ending the inbound stream. Closes #191

* Add a simple success response to API requests

* Add viewers over time API

* Move controllers to admin directory

controllers/admin/serverConfig.go

@@ -1,4 +1,4 @@
-package controllers
+package admin
 
 import (
 	"encoding/json"

controllers/admin/viewers.go

@@ -0,0 +1,15 @@
+package admin
+
+import (
+	"encoding/json"
+	"net/http"
+
+	"github.com/gabek/owncast/metrics"
+)
+
+// GetViewersOverTime will return the number of viewers at points in time
+func GetViewersOverTime(w http.ResponseWriter, r *http.Request) {
+	viewersOverTime := metrics.Metrics.Viewers
+	w.Header().Set("Content-Type", "application/json")
+	json.NewEncoder(w).Encode(viewersOverTime)
+}