GRA-1298: License check changes, free tier limits for saas (#2418)

* set free tier limits through config

* add host limit to config

* check for host limit on free tier

* fix license validation, replace node limit with hosts

* add hosts to telemetry data

* debug init

* validate license every 1hr

* hook manager, api to fetch server usage

* hook manager, server usage api

* encode json server usage api

* update ngork url

* update license validation endpoint

* avoid setting limits on eer

* adding hotfix

* correct users limits env var

* add comments to exported funcs

---------

Co-authored-by: afeiszli <alex.feiszli@gmail.com>

models/structs.go

@@ -2,6 +2,7 @@ package models
 
 import (
 	"strings"
+	"time"
 
 	jwt "github.com/golang-jwt/jwt/v4"
 	"golang.zx2c4.com/wireguard/wgctrl/wgtypes"
@@ -274,3 +275,18 @@ type StunServer struct {
 	Domain string `json:"domain" yaml:"domain"`
 	Port   int    `json:"port" yaml:"port"`
 }
+
+// HookDetails - struct to hold hook info
+type HookDetails struct {
+	Hook     func() error
+	Interval time.Duration
+}
+
+// LicenseLimits - struct license limits
+type LicenseLimits struct {
+	Servers  int `json:"servers"`
+	Users    int `json:"users"`
+	Hosts    int `json:"hosts"`
+	Clients  int `json:"clients"`
+	Networks int `json:"networks"`
+}