Premium SKU (#30396)

* Added premium SKU

* removed duplicate enterprise license check functions

* Added license check on API layer

* lint fix

* lint fix

* refactured signature:

* test: Add comprehensive tests for license tier check functions

* fixed test

* text update

* optimised license checks

* fixedf test

* Updated license valid function

* webapp license checks

* handling prekium SKU in webappp:

* added plugin api method and general refactoring

* Updated tests

---------

Co-authored-by: Mattermost Build <build@mattermost.com>

server/platform/services/telemetry/telemetry.go

@@ -99,6 +99,7 @@ type TrackSKU string
 const (
 	TrackProfessionalSKU TrackSKU = "professional"
 	TrackEnterpriseSKU   TrackSKU = "enterprise"
+	TrackPremiumSKU      TrackSKU = "premium"
 )
 
 type TrackFeature string