Service environment (#23443)

* fix fileutils.TestFindFile on MacOS

* introduce model.ExternalServiceEnvironment

* pick license public key from external service env

* pick Stripe public key from external service env

* pick Rudder key from external service env

* configure Sentry DSN from external service env

* always log external_service_environment, Unsetenv

* clear faked BuildEnv, improve logging

* strip out unset GOTAGS

* fix Sentry tests

* simplify to just ServiceEnvironment

* relocate ServiceEnvironment in client config

* initialize CWS URLs based on service environment

* unset rudder key for boards dev

* harden service environment to avoid accidental production

* fix TestSentry again

* fix DEFAULT -> ENTERPRISE

* s/dev/test when naming playbooks rudder key

* simplify boards rudder key switch

* use uniform rudderKey variable names

* retain compatibility with existing pipeline

* reduce to just production/test

* unit test with valid test license

* simplify Playbooks telemetry initialization

* restore dev service environment

* emit ServiceEnvironment when running e2e tests

server/public/model/service_environment.go

@@ -0,0 +1,45 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package model
+
+import (
+	"os"
+	"strings"
+)
+
+const (
+	// ServiceEnvironmentProduction represents the production self-managed or cloud
+	// environments. This can be configured explicitly with MM_SERVICEENVIRONMENT explicitly
+	// set to "production", but is also the default for any production builds.
+	ServiceEnvironmentProduction = "production"
+	// ServiceEnvironmentTest represents testing environments in which MM_SERVICEENVIRONMENT
+	// is set explicitly to "test".
+	ServiceEnvironmentTest = "test"
+	// ServiceEnvironmentDev represents development environments. This can be configured
+	// explicitly with MM_SERVICEENVIRONMENT set to "dev", but is also the default for any
+	// non-production builds.
+	ServiceEnvironmentDev = "dev"
+)
+
+// GetServiceEnvironment returns the currently configured external service environment,
+// deciding which public key is used to validate enterprise licenses, which telemetry keys are
+// active, and which Stripe keys are in use.
+//
+// To configure an environment other than default, set MM_SERVICEENVIRONMENT before
+// starting the application. Production builds default to ServiceEnvironmentProduction, and
+// non-production builds default to ServiceEnvironmentDev.
+//
+// Note that this configuration is explicitly not part of the model.Config data structure, as it
+// should never be persisted to the config store nor accidentally configured in any other way than
+// the MM_SERVICEENVIRONMENT variable.
+func GetServiceEnvironment() string {
+	externalServiceEnvironment := strings.TrimSpace(strings.ToLower(os.Getenv("MM_SERVICEENVIRONMENT")))
+
+	switch externalServiceEnvironment {
+	case ServiceEnvironmentProduction, ServiceEnvironmentTest, ServiceEnvironmentDev:
+		return externalServiceEnvironment
+	}
+
+	return getDefaultServiceEnvironment()
+}