Check license expiration, disable license and notify administrator (#14420)

* Check license expiration and notify administrator

model/license.go

@@ -12,6 +12,8 @@ import (
 const (
 	EXPIRED_LICENSE_ERROR = "api.license.add_license.expired.app_error"
 	INVALID_LICENSE_ERROR = "api.license.add_license.invalid.app_error"
+	LICENSE_GRACE_PERIOD  = 1000 * 60 * 60 * 24 * 10 //10 days
+	LICENSE_RENEWAL_LINK  = "https://licensing.mattermost.com/renew"
 )
 
 type LicenseRecord struct {
@@ -194,6 +196,11 @@ func (l *License) IsExpired() bool {
 	return l.ExpiresAt < GetMillis()
 }
 
+func (l *License) IsPastGracePeriod() bool {
+	timeDiff := GetMillis() - l.ExpiresAt
+	return timeDiff > LICENSE_GRACE_PERIOD
+}
+
 func (l *License) IsStarted() bool {
 	return l.StartsAt < GetMillis()
 }