update all dependencies (maven artifacts)

- PDF dependency was missing in the pom file the JDK8
  * We should think about creating a parent pom - in that case all plantuml dependencies could be in the parent pom and we would only the mantain one pom file.
    (It is also possible to drop the Java 8 support.)
  * Why do we not have any PDF tests?
- add rule to ignore version update hint with `-dev` followed by a dot and date (e.g. `0.37.0-dev.20230308`)
- migration from JUnit4 to JUnit5

src/test/java/net/sourceforge/plantuml/servlet/TestOldProxy.java

@@ -4,6 +4,9 @@ import java.io.IOException;
 import java.net.HttpURLConnection;
 import java.net.URL;
 
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
 import net.sourceforge.plantuml.servlet.utils.WebappTestCase;
 
 
@@ -12,59 +15,61 @@ public class TestOldProxy extends WebappTestCase {
     /**
      * Verifies the proxified reception of the default Bob and Alice diagram
      */
+    @Test
     public void testDefaultProxy() throws IOException {
         final URL url = new URL(getServerUrl() + "/proxy/" + getTestDiagramUrl());
         final HttpURLConnection conn = (HttpURLConnection)url.openConnection();
         // Analyze response
         // Verifies HTTP status code and the Content-Type
-        assertEquals("Bad HTTP status received", 200, conn.getResponseCode());
-        assertEquals(
-            "Response content type is not PNG",
+        Assertions.assertEquals(200, conn.getResponseCode(), "Bad HTTP status received");
+        Assertions.assertEquals(
             "image/png",
-            conn.getContentType().toLowerCase()
+            conn.getContentType().toLowerCase(),
+            "Response content type is not PNG"
         );
         // Get the image and verify its size (~2000 bytes)
         byte[] inMemoryImage = getContentAsBytes(conn);
         int diagramLen = inMemoryImage.length;
-        assertTrue(diagramLen > 2000);
-        assertTrue(diagramLen < 3000);
+        Assertions.assertTrue(diagramLen > 2000);
+        Assertions.assertTrue(diagramLen < 3000);
     }
 
+    /**
+     * Verifies the proxified reception of the default Bob and Alice diagram in a specific format (SVG)
+     */
+    @Test
     public void testProxyWithFormat() throws IOException {
         final URL url = new URL(getServerUrl() + "/proxy/svg/" + getTestDiagramUrl());
         final HttpURLConnection conn = (HttpURLConnection)url.openConnection();
         // Analyze response
         // Verifies HTTP status code and the Content-Type
-        assertEquals("Bad HTTP status received", 200, conn.getResponseCode());
-        assertEquals(
-            "Response content type is not SVG",
+        Assertions.assertEquals(200, conn.getResponseCode(), "Bad HTTP status received");
+        Assertions.assertEquals(
             "image/svg+xml",
-            conn.getContentType().toLowerCase()
+            conn.getContentType().toLowerCase(),
+            "Response content type is not SVG"
         );
         // Get the content and verify its size
         String diagram = getContentText(conn);
         int diagramLen = diagram.length();
-        assertTrue(diagramLen > 1000);
-        assertTrue(diagramLen < 3000);
+        Assertions.assertTrue(diagramLen > 1000);
+        Assertions.assertTrue(diagramLen < 3000);
     }
 
     /**
      * Verifies that the HTTP header of a diagram incites the browser to cache it.
      */
+    @Test
     public void testInvalidUrl() throws IOException {
         final URL url = new URL(getServerUrl() + "/proxy/invalidURL");
         final HttpURLConnection conn = (HttpURLConnection)url.openConnection();
         // Analyze response
         // Check if status code is 400
-        assertEquals(
-            "Bad HTTP status received",
-            400,
-            conn.getResponseCode()
-        );
+        Assertions.assertEquals(400, conn.getResponseCode(), "Bad HTTP status received");
         // Check error message
-        assertTrue(
-            "Response is not malformed URL",
-            getContentText(conn.getErrorStream()).contains("URL malformed.")
+        Assertions.assertTrue(
+            getContentText(conn.getErrorStream()).contains("URL malformed."),
+            "Response is not malformed URL"
         );
     }