[CLD-6894] Add 60, 30, and 7 day reminder emails for Cloud Renewals (#25883)

* Add email notifications for Cloud Renewals

* Updates

* Updates

* Update app-layers

* make build-templates

* Add ability to set an env variable as a unix timestamp in s as the current date when getting DaysToExpiration

* Add a mechanism to ensure at least one admin receives every email

---------

Co-authored-by: Mattermost Build <build@mattermost.com>
Co-authored-by: Gabe Jackson <3694686+gabrieljackson@users.noreply.github.com>

server/public/model/cloud.go

@@ -5,7 +5,10 @@ package model
 
 import (
 	"encoding/json"
+	"os"
+	"strconv"
 	"strings"
+	"time"
 )
 
 const (
@@ -184,6 +187,21 @@ type Subscription struct {
 	WillRenew               string   `json:"will_renew"`
 }
 
+func (s *Subscription) DaysToExpiration() int64 {
+	now := time.Now().UnixMilli()
+	// Allows us to base the current time off of an environment variable for testing purposes
+	if GetServiceEnvironment() == ServiceEnvironmentTest {
+		if currTime, set := os.LookupEnv("CLOUD_MOCK_CURRENT_TIME"); set {
+			timeInt, err := strconv.ParseInt(currTime, 10, 64)
+			if err == nil {
+				now = time.Unix(timeInt, 0).UnixMilli()
+			}
+		}
+	}
+	daysToExpiry := (s.EndAt - now) / (1000 * 60 * 60 * 24)
+	return daysToExpiry
+}
+
 // Subscription History model represents true up event in a yearly subscription
 type SubscriptionHistory struct {
 	ID             string `json:"id"`

server/public/model/system.go

@@ -38,6 +38,7 @@ const (
 	SystemHostedPurchaseNeedsScreening     = "HostedPurchaseNeedsScreening"
 	AwsMeteringReportInterval              = 1
 	AwsMeteringDimensionUsageHrs           = "UsageHrs"
+	CloudRenewalEmail                      = "CloudRenewalEmail"
 )
 
 const (