Add copy-to-clipboard button to /success

token-grabber/src/main/resources/templates/success.html

@@ -18,7 +18,14 @@
         </tr>
         <tr>
             <th scope="row">accessToken</th>
-            <td> <textarea readonly th:text="${accessToken}"></textarea></td>
+            <td>
+                <textarea id="accessTokenTextArea" readonly th:text="${accessToken}"></textarea>
+                <br>
+                <button class="btn btn-outline-primary"
+                        onclick="navigator.clipboard.writeText(document.getElementById('accessTokenTextArea').value)">
+                Copy to clipboard
+                </button>
+            </td>
         </tr>
         </tbody>
     </table>