Chore: Pass signed user_hash to Intercom via Rudderstack (#63921)

* move analytics identifiers to backend

* implement hash function

* grab secret from env

* expose and retrieve intercom secret from config

* concat email with appUrl to ensure uniqueness

* revert to just using email

* Revert "revert to just using email"

This reverts commit 8f10f9b1bc.

* add docstring

pkg/setting/setting.go

@@ -401,6 +401,7 @@ type Cfg struct {
 	RudderstackWriteKey                 string
 	RudderstackSDKURL                   string
 	RudderstackConfigURL                string
+	IntercomSecret                      string
 
 	// AzureAD
 	AzureADSkipOrgRoleSync bool
@@ -1034,6 +1035,7 @@ func (cfg *Cfg) Load(args CommandLineArgs) error {
 	cfg.RudderstackDataPlaneURL = analytics.Key("rudderstack_data_plane_url").String()
 	cfg.RudderstackSDKURL = analytics.Key("rudderstack_sdk_url").String()
 	cfg.RudderstackConfigURL = analytics.Key("rudderstack_config_url").String()
+	cfg.IntercomSecret = analytics.Key("intercom_secret").String()
 
 	cfg.ReportingEnabled = analytics.Key("reporting_enabled").MustBool(true)
 	cfg.ReportingDistributor = analytics.Key("reporting_distributor").MustString("grafana-labs")