Feat twitch livestreams (#334)

* backend code

* fixed twitch authentication

server/twitch/rest.go

@@ -0,0 +1,40 @@
+package twitch
+
+import (
+	"encoding/json"
+	"net/http"
+	"slices"
+)
+
+type addUserReq struct {
+	User string `json:"user"`
+}
+
+func MonitorUserHandler(m *Monitor) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		var req addUserReq
+
+		if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+			return
+		}
+
+		m.Add(req.User)
+
+		if err := json.NewEncoder(w).Encode("ok"); err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+			return
+		}
+	}
+}
+
+func GetMonitoredUsers(m *Monitor) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		it := m.GetMonitoredUsers()
+
+		if err := json.NewEncoder(w).Encode(slices.Collect(it)); err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+			return
+		}
+	}
+}