[MM-27535] User invite limits for MM Cloud (#15197)

* Add a config for MM User Limit

* Adding graceful errors for if an administrator invites people passed their user limit

* Including changed vendor files

* Adding unit test

* Fix a bug

* Push up working tests (Thanks Joram)

* Add more cases, clean up logs in code

* One more case

* Refactoring based on PR comments

* Updating i18n

* Some changes based on PR review

* Remove a comment

* Bring back some translations that were somehow removed

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

model/config.go

@@ -861,6 +861,7 @@ type ExperimentalSettings struct {
 	EnableClickToReply              *bool  `restricted:"true"`
 	LinkMetadataTimeoutMilliseconds *int64 `restricted:"true"`
 	RestrictSystemAdmin             *bool  `restricted:"true"`
+	CloudUserLimit                  *int64 `restricted:"true"`
 	UseNewSAMLLibrary               *bool
 }
 
@@ -884,6 +885,11 @@ func (s *ExperimentalSettings) SetDefaults() {
 	if s.RestrictSystemAdmin == nil {
 		s.RestrictSystemAdmin = NewBool(false)
 	}
+
+	if s.CloudUserLimit == nil {
+		// User limit 0 is treated as no limit
+		s.CloudUserLimit = NewInt64(0)
+	}
 	if s.UseNewSAMLLibrary == nil {
 		s.UseNewSAMLLibrary = NewBool(false)
 	}