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/handlers.go

@@ -238,10 +238,6 @@ func requireLicense(c *Context) *model.AppError {
 	return nil
 }
 
-func minimumProfessionalLicense(c *Context) *model.AppError {
-	return model.MinimumProfessionalProvidedLicense(c.App.Srv().License())
-}
-
 func setHandlerOpts(handler *web.Handler, opts ...APIHandlerOption) {
 	if len(opts) == 0 {
 		return