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/channels/api4/group.go

@@ -1482,7 +1482,7 @@ func licensedAndConfiguredForGroupBySource(app *app.App, source model.GroupSourc
 		return model.NewAppError("", "api.ldap_groups.license_error", nil, "", http.StatusForbidden)
 	}
 
-	if source == model.GroupSourceCustom && lic.SkuShortName != model.LicenseShortSkuProfessional && lic.SkuShortName != model.LicenseShortSkuEnterprise {
+	if source == model.GroupSourceCustom && !model.MinimumProfessionalLicense(lic) {
 		return model.NewAppError("", "api.custom_groups.license_error", nil, "", http.StatusBadRequest)
 	}