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/outgoing_oauth_connection.go

@@ -63,7 +63,7 @@ func ensureOutgoingOAuthConnectionInterface(c *Context, where string) (einterfac
 		return nil, false
 	}
 
-	if c.App.OutgoingOAuthConnections() == nil || c.App.License() == nil || c.App.License().SkuShortName != model.LicenseShortSkuEnterprise {
+	if c.App.OutgoingOAuthConnections() == nil || !model.MinimumEnterpriseLicense(c.App.License()) {
 		c.Err = model.NewAppError(where, "api.license.upgrade_needed.app_error", nil, "", http.StatusNotImplemented)
 		return nil, false
 	}