Refactor: Make check results map threadsafe

CityDoctorParent/CityDoctorModel/src/main/java/de/hft/stuttgart/citydoctor2/check/Checkable.java

@@ -20,9 +20,9 @@ package de.hft.stuttgart.citydoctor2.check;
 
 import java.io.Serial;
 import java.io.Serializable;
-import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
 
 import de.hft.stuttgart.citydoctor2.utils.CheckErrorFound;
 import de.hft.stuttgart.citydoctor2.utils.visitors.CheckableErrorCollector;
@@ -49,7 +49,7 @@ public abstract class Checkable implements Serializable {
 
 	private static final Logger logger = LogManager.getLogger(Checkable.class);
 
-	private final Map<CheckId, CheckResult> checkResults = new HashMap<>();
+	private final Map<CheckId, CheckResult> checkResults = new ConcurrentHashMap<>();
 	private boolean isValidated = false;
 
 	public void setValidated(boolean validated) {