Outbound live stream notifications (#1663)

* First pass at browser, discord, twilio notifications

* Commit updated Javascript packages

* Remove twilio notification support

* Email notifications/smtp support

* Fix Firefox notification support, remove chrome checks

* WIP more email work

* Add support for twitter notifications

* Add stream title to discord and twitter notifications

* Update notification registration modal

* Fix hide/show email section

* Commit updated API documentation

* Commit updated Javascript packages

* Fix post-rebase missing var

* Remove unused var

* Handle unsubscribe errors for browser push

* Standardize email config prop names

* Allow overriding go live email template

* Some notifications cleanup

* Commit updated Javascript packages

* Remove email/smtp/mailjet support

* Remove more references to email notifications

Co-authored-by: Owncast <owncast@owncast.online>

controllers/notifications.go

@@ -0,0 +1,50 @@
+package controllers
+
+import (
+	"encoding/json"
+	"net/http"
+
+	"github.com/owncast/owncast/notifications"
+
+	"github.com/owncast/owncast/utils"
+
+	log "github.com/sirupsen/logrus"
+)
+
+// RegisterForLiveNotifications will register a channel + destination to be
+// notified when a stream goes live.
+func RegisterForLiveNotifications(w http.ResponseWriter, r *http.Request) {
+	if r.Method != POST {
+		WriteSimpleResponse(w, false, r.Method+" not supported")
+		return
+	}
+
+	type request struct {
+		// Channel is the notification channel (browser, sms, etc)
+		Channel string `json:"channel"`
+		// Destination is the target of the notification in the above channel.
+		Destination string `json:"destination"`
+	}
+
+	decoder := json.NewDecoder(r.Body)
+	var req request
+	if err := decoder.Decode(&req); err != nil {
+		log.Errorln(err)
+		WriteSimpleResponse(w, false, "unable to register for notifications")
+		return
+	}
+
+	// Make sure the requested channel is one we want to handle.
+	validTypes := []string{notifications.BrowserPushNotification}
+	_, validChannel := utils.FindInSlice(validTypes, req.Channel)
+	if !validChannel {
+		WriteSimpleResponse(w, false, "invalid notification channel: "+req.Channel)
+		return
+	}
+
+	if err := notifications.AddNotification(req.Channel, req.Destination); err != nil {
+		log.Errorln(err)
+		WriteSimpleResponse(w, false, "unable to save notification")
+		return
+	}
+}