Enable async support for servlets

gradle/changelog/async.yaml

@@ -0,0 +1,2 @@
+- type: fixed
+  description: Async support for servlets is now enabled

scm-webapp/src/main/webapp/WEB-INF/web.xml

@@ -14,11 +14,11 @@
     You should have received a copy of the GNU Affero General Public License
     along with this program. If not, see https://www.gnu.org/licenses/.
 -->
-<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"
+<web-app version="3.0" xmlns="http://java.sun.com/xml/ns/javaee"
          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-         xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" 
+         xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
          metadata-complete="true">
-    
+
   <display-name>SCM-Manager ${project.version}</display-name>
 
   <!-- bootstrapping -->
@@ -26,6 +26,7 @@
   <filter>
     <filter-name>BootstrapFilter</filter-name>
     <filter-class>sonia.scm.lifecycle.BootstrapContextFilter</filter-class>
+    <async-supported>true</async-supported>
   </filter>
 
   <filter-mapping>
@@ -42,5 +43,5 @@
   <session-config>
     <session-timeout>30</session-timeout>
   </session-config>
-    
+
 </web-app>