[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/channels/app/cloud.go

@@ -8,11 +8,13 @@ import (
 	"fmt"
 	"io"
 	"net/http"
+	"strconv"
 	"time"
 
 	"github.com/mattermost/mattermost/server/public/model"
 	"github.com/mattermost/mattermost/server/public/shared/mlog"
 	"github.com/mattermost/mattermost/server/v8/channels/product"
+	"github.com/mattermost/mattermost/server/v8/channels/store"
 	"github.com/mattermost/mattermost/server/v8/einterfaces"
 )
 
@@ -266,3 +268,98 @@ func (a *App) SendSubscriptionHistoryEvent(userID string) (*model.SubscriptionHi
 	}
 	return a.Cloud().CreateOrUpdateSubscriptionHistoryEvent(userID, int(userCount))
 }
+
+func (a *App) DoSubscriptionRenewalCheck() {
+	if !a.License().IsCloud() || !a.Config().FeatureFlags.CloudAnnualRenewals {
+		return
+	}
+
+	subscription, err := a.Cloud().GetSubscription("")
+	if err != nil {
+		a.Log().Error("Error getting subscription", mlog.Err(err))
+		return
+	}
+
+	if subscription == nil {
+		a.Log().Error("Subscription not found")
+		return
+	}
+
+	sysVar, err := a.Srv().Store().System().GetByName(model.CloudRenewalEmail)
+	if err != nil {
+		// We only care about the error if it wasn't a not found error
+		if _, ok := err.(*store.ErrNotFound); !ok {
+			a.Log().Error(err.Error())
+		}
+	}
+
+	prevSentEmail := int64(0)
+	if sysVar != nil {
+		// We don't care about parse errors because it's possible the value is empty, and we've already defaulted to 0
+		prevSentEmail, _ = strconv.ParseInt(sysVar.Value, 10, 64)
+	}
+
+	if subscription.WillRenew == "true" {
+		// They've already completed the renewal process so no need to email them.
+		// We can zero out the system variable so that this process will work again next year
+		if prevSentEmail != 0 {
+			sysVar.Value = "0"
+			err = a.Srv().Store().System().SaveOrUpdate(sysVar)
+			if err != nil {
+				a.Log().Error("Error saving system variable", mlog.Err(err))
+			}
+		}
+		return
+	}
+
+	var emailFunc func(email, locale, siteURL string) error
+
+	daysToExpiration := subscription.DaysToExpiration()
+
+	// Only send the email if within the period and it's not already been sent
+	// This allows the email to send on day 59 if for whatever reason it was unable to on day 60
+	if daysToExpiration <= 60 && daysToExpiration > 30 && prevSentEmail != 60 {
+		emailFunc = a.Srv().EmailService.SendCloudRenewalEmail60
+		prevSentEmail = 60
+	} else if daysToExpiration <= 30 && daysToExpiration > 7 && prevSentEmail != 30 {
+		emailFunc = a.Srv().EmailService.SendCloudRenewalEmail30
+		prevSentEmail = 30
+	} else if daysToExpiration <= 7 && daysToExpiration > 3 && prevSentEmail != 7 {
+		emailFunc = a.Srv().EmailService.SendCloudRenewalEmail7
+		prevSentEmail = 7
+	}
+
+	if emailFunc == nil {
+		return
+	}
+
+	sysAdmins, aErr := a.getSysAdminsEmailRecipients()
+	if aErr != nil {
+		a.Log().Error("Error getting sys admins", mlog.Err(aErr))
+		return
+	}
+
+	numFailed := 0
+	for _, admin := range sysAdmins {
+		err = emailFunc(admin.Email, admin.Locale, *a.Config().ServiceSettings.SiteURL)
+		if err != nil {
+			a.Log().Error("Error sending renewal email", mlog.Err(err))
+			numFailed += 1
+		}
+	}
+
+	if numFailed == len(sysAdmins) {
+		// If all emails failed, we don't want to update the system variable
+		return
+	}
+
+	updatedSysVar := &model.System{
+		Name:  model.CloudRenewalEmail,
+		Value: strconv.FormatInt(prevSentEmail, 10),
+	}
+
+	err = a.Srv().Store().System().SaveOrUpdate(updatedSysVar)
+	if err != nil {
+		a.Log().Error("Error saving system variable", mlog.Err(err))
+	}
+}