Add metric warning support (announcement bar and DM) (#14483)

* Admin. Advisory: Add warning for number of active users metric status

Co-authored-by: Catalin Tomai <catalin.tomai@mattermost.com>

api4/system.go

@@ -54,6 +54,9 @@ func (api *API) InitSystem() {
 	api.BaseRoutes.ApiRoot.Handle("/server_busy", api.ApiSessionRequired(setServerBusy)).Methods("POST")
 	api.BaseRoutes.ApiRoot.Handle("/server_busy", api.ApiSessionRequired(getServerBusyExpires)).Methods("GET")
 	api.BaseRoutes.ApiRoot.Handle("/server_busy", api.ApiSessionRequired(clearServerBusy)).Methods("DELETE")
+
+	api.BaseRoutes.ApiRoot.Handle("/warn_metrics/status", api.ApiSessionRequired(getWarnMetricsStatus)).Methods("GET")
+	api.BaseRoutes.ApiRoot.Handle("/warn_metrics/ack/{warn_metric_id:[A-Za-z0-9-_]+}", api.ApiHandler(sendWarnMetricAckEmail)).Methods("POST")
 }
 
 func getSystemPing(c *Context, w http.ResponseWriter, r *http.Request) {
@@ -544,3 +547,61 @@ func getServerBusyExpires(c *Context, w http.ResponseWriter, r *http.Request) {
 	}
 	w.Write([]byte(c.App.Srv().Busy.ToJson()))
 }
+
+func getWarnMetricsStatus(c *Context, w http.ResponseWriter, r *http.Request) {
+	if !c.App.SessionHasPermissionTo(*c.App.Session(), model.PERMISSION_MANAGE_SYSTEM) {
+		c.SetPermissionError(model.PERMISSION_MANAGE_SYSTEM)
+		return
+	}
+
+	license := c.App.Srv().License()
+	if license != nil {
+		mlog.Debug("License is present, skip.")
+		return
+	}
+
+	status, err := c.App.GetWarnMetricsStatus()
+	if err != nil {
+		c.Err = err
+		return
+	}
+
+	w.Write([]byte(model.MapWarnMetricStatusToJson(status)))
+}
+
+func sendWarnMetricAckEmail(c *Context, w http.ResponseWriter, r *http.Request) {
+	auditRec := c.MakeAuditRecord("sendWarnMetricAckEmail", audit.Fail)
+	defer c.LogAuditRec(auditRec)
+	c.LogAudit("attempt")
+
+	if !c.App.SessionHasPermissionTo(*c.App.Session(), model.PERMISSION_MANAGE_SYSTEM) {
+		c.SetPermissionError(model.PERMISSION_MANAGE_SYSTEM)
+		return
+	}
+
+	license := c.App.Srv().License()
+	if license != nil {
+		mlog.Debug("License is present, skip.")
+		return
+	}
+
+	user, appErr := c.App.GetUser(c.App.Session().UserId)
+	if appErr != nil {
+		c.Err = appErr
+		return
+	}
+
+	ack := model.SendWarnMetricAckFromJson(r.Body)
+	if ack == nil {
+		c.SetInvalidParam("ack")
+		return
+	}
+
+	appErr = c.App.NotifyAndSetWarnMetricAck(c.Params.WarnMetricId, user, ack.ForceAck, false)
+	if appErr != nil {
+		c.Err = appErr
+	}
+
+	auditRec.Success()
+	ReturnStatusOK(w)
+}