MM-8607 Add ability to turn off non-critical services when under load (#13212)

* MM-8607: add ability to turn off non-critical services under load

* server busy invalid param unit tests

* MM-8607: rename server busy endpoints

* MM-8607: handle case where App not initialized

* MM-8607: additional unit test cases per feedback.

* MM-8607: use decorator to check isbusy when adding endpoint route

* MM-8607: rename endpoints, use struct for json

* Update api4/system.go

Fix misspelled log output

Co-Authored-By: Saturnino Abril <saturnino.abril@gmail.com>

* MM-8607: fix i18n order; max seconds for server busy expiry

model/utils.go

@@ -207,7 +207,7 @@ func MapToJson(objmap map[string]string) string {
 	return string(b)
 }
 
-// MapToJson converts a map to a json string
+// MapBoolToJson converts a map to a json string
 func MapBoolToJson(objmap map[string]bool) string {
 	b, _ := json.Marshal(objmap)
 	return string(b)