feat: Introduce Playwright for UI testing

Instead of using Robot Framework which does not run during a `mvn install`. Playwright seems to be the better approach. We can now write them as normal JUnit test and they are executed during a build.

Additionally this PR solves some interesting bugs found during writing Playwright tests:

- A reset of a lesson removes all assignments as a result another user wouldn't see any assignments
- If someone solves an assignment the assignment automatically got solved for a new user since the assignment included the `solved` flag which immediately got copied to new lesson progress.
- Introduction of assignment progress linking a assignment not directly to all users.

src/it/java/org/owasp/webgoat/integration/ProgressRaceConditionIntegrationTest.java

@@ -0,0 +1,57 @@
+package org.owasp.webgoat.integration;
+
+import io.restassured.RestAssured;
+import io.restassured.response.Response;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.Callable;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.stream.Collectors;
+import java.util.stream.IntStream;
+import org.assertj.core.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+public class ProgressRaceConditionIntegrationTest extends IntegrationTest {
+
+  @Test
+  public void runTests() throws InterruptedException {
+    int NUMBER_OF_CALLS = 40;
+    int NUMBER_OF_PARALLEL_THREADS = 5;
+    startLesson("Challenge1");
+
+    Callable<Response> call =
+        () -> {
+          // System.out.println("thread "+Thread.currentThread().getName());
+          return RestAssured.given()
+              .when()
+              .relaxedHTTPSValidation()
+              .cookie("JSESSIONID", getWebGoatCookie())
+              .formParams(Map.of("flag", "test"))
+              .post(url("challenge/flag/1"));
+        };
+    ExecutorService executorService = Executors.newFixedThreadPool(NUMBER_OF_PARALLEL_THREADS);
+    List<? extends Callable<Response>> flagCalls =
+        IntStream.range(0, NUMBER_OF_CALLS).mapToObj(i -> call).collect(Collectors.toList());
+    var responses = executorService.invokeAll(flagCalls);
+
+    // A certain amount of parallel calls should fail as optimistic locking in DB is applied
+    long countStatusCode500 =
+        responses.stream()
+            .filter(
+                r -> {
+                  try {
+                    // System.err.println(r.get().getStatusCode());
+                    return r.get().getStatusCode() != 200;
+                  } catch (InterruptedException | ExecutionException e) {
+                    // System.err.println(e);
+                    throw new IllegalStateException(e);
+                  }
+                })
+            .count();
+    System.err.println("counted status 500: " + countStatusCode500);
+    Assertions.assertThat(countStatusCode500)
+        .isLessThanOrEqualTo((NUMBER_OF_CALLS - (NUMBER_OF_CALLS / NUMBER_OF_PARALLEL_THREADS)));
+  }
+}