AgentNext.END constant and bump version to 1.5.6

pom.xml

@@ -4,7 +4,7 @@
 	<artifactId>lm-lib</artifactId>
 	<groupId>de.extio</groupId>
 	<name>lm-lib</name>
-	<version>1.5.5</version>
+	<version>1.5.6</version>
 	
 	<properties>
 		<java.version>21</java.version>

src/main/java/de/extio/lmlib/agent/AgentNext.java

@@ -2,4 +2,6 @@ package de.extio.lmlib.agent;
 
 public final record AgentNext(String name, Boolean gradingPassed) {
 	
+    public static final AgentNext END = new AgentNext(null, null);
+
 }

src/main/java/de/extio/lmlib/agent/BaseAgent.java

@@ -70,7 +70,7 @@ public interface BaseAgent {
 	}
 	
 	default AgentNext chooseNext(final AgentContext context) {
-		return new AgentNext(null, null);
+		return AgentNext.END;
 	}
 	
 	default List<AgentContext> execute(final Client client, final ExecutorService agentExecutorService, final AgentContext context) {

src/test/java/de/extio/lmlib/agent/AgentTest.java

@@ -100,7 +100,7 @@ public class AgentTest {
 						},
 						null,
 						null,
-						context -> new AgentNext(null, null)));
+						context -> AgentNext.END));
 		
 		final var context = new AgentContext(agents);
 		context.getContext().put("code", List.of(Files.readString(Path.of("src/main/java/de/extio/lmlib/agent/Agent.java"))));