[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/email/mocks/ServiceInterface.go

@@ -128,6 +128,48 @@ func (_m *ServiceInterface) SendChangeUsernameEmail(newUsername string, _a1 stri
 	return r0
 }
 
+// SendCloudRenewalEmail30 provides a mock function with given fields: _a0, locale, siteURL
+func (_m *ServiceInterface) SendCloudRenewalEmail30(_a0 string, locale string, siteURL string) error {
+	ret := _m.Called(_a0, locale, siteURL)
+
+	var r0 error
+	if rf, ok := ret.Get(0).(func(string, string, string) error); ok {
+		r0 = rf(_a0, locale, siteURL)
+	} else {
+		r0 = ret.Error(0)
+	}
+
+	return r0
+}
+
+// SendCloudRenewalEmail60 provides a mock function with given fields: _a0, locale, siteURL
+func (_m *ServiceInterface) SendCloudRenewalEmail60(_a0 string, locale string, siteURL string) error {
+	ret := _m.Called(_a0, locale, siteURL)
+
+	var r0 error
+	if rf, ok := ret.Get(0).(func(string, string, string) error); ok {
+		r0 = rf(_a0, locale, siteURL)
+	} else {
+		r0 = ret.Error(0)
+	}
+
+	return r0
+}
+
+// SendCloudRenewalEmail7 provides a mock function with given fields: _a0, locale, siteURL
+func (_m *ServiceInterface) SendCloudRenewalEmail7(_a0 string, locale string, siteURL string) error {
+	ret := _m.Called(_a0, locale, siteURL)
+
+	var r0 error
+	if rf, ok := ret.Get(0).(func(string, string, string) error); ok {
+		r0 = rf(_a0, locale, siteURL)
+	} else {
+		r0 = ret.Error(0)
+	}
+
+	return r0
+}
+
 // SendCloudUpgradeConfirmationEmail provides a mock function with given fields: userEmail, name, trialEndDate, locale, siteURL, workspaceName, isYearly, embeddedFiles
 func (_m *ServiceInterface) SendCloudUpgradeConfirmationEmail(userEmail string, name string, trialEndDate string, locale string, siteURL string, workspaceName string, isYearly bool, embeddedFiles map[string]io.Reader) error {
 	ret := _m.Called(userEmail, name, trialEndDate, locale, siteURL, workspaceName, isYearly, embeddedFiles)