implement purge db command

service/src/main/java/CTFApplication.java

 import auth.ExampleAuthenticator;
 import com.bazaarvoice.dropwizard.webjars.WebJarBundle;
+import com.fasterxml.jackson.dataformat.yaml.snakeyaml.Yaml;
 import com.google.inject.AbstractModule;
 import com.google.inject.Guice;
 import com.google.inject.Injector;
 import com.mongodb.MongoClient;
+import commands.PurgeDatabaseCommand;
 import core.ApplicationConfiguration;
 import io.dropwizard.Application;
 import io.dropwizard.assets.AssetsBundle;
@@ -37,6 +39,7 @@ public class CTFApplication extends Application<ApplicationConfiguration>
     public void initialize(final Bootstrap<ApplicationConfiguration> bootstrap)
     {
         bootstrap.addBundle(new AssetsBundle("/assets", "/page", "index.html"));
+        bootstrap.addCommand(new PurgeDatabaseCommand());
         Stream.of("org.webjars.npm", "org.webjars.bower")
                 .map(WebJarBundle::new)
                 .forEach(bootstrap::addBundle);
@@ -100,7 +103,7 @@ public class CTFApplication extends Application<ApplicationConfiguration>
                 bind(ApplicationConfiguration.class).toInstance(applicationConfiguration); //todo: refactor
 
                 Morphia morphia = new Morphia();
-                morphia.mapPackage("objects.Team");
+                morphia.mapPackage("objects.Team"); //todo? what for?
                 datastore = morphia.createDatastore(
                         new MongoClient(applicationConfiguration.getDbHost(),applicationConfiguration.getDbPort()), applicationConfiguration.getDbName());
                 datastore.ensureIndexes();

service/src/main/java/commands/PurgeDatabaseCommand.java

+package commands;
+
+import com.mongodb.MongoClient;
+import core.ApplicationConfiguration;
+import io.dropwizard.cli.ConfiguredCommand;
+import io.dropwizard.setup.Bootstrap;
+import net.sourceforge.argparse4j.inf.Namespace;
+import org.mongodb.morphia.Datastore;
+import org.mongodb.morphia.Morphia;
+
+public class PurgeDatabaseCommand extends ConfiguredCommand<ApplicationConfiguration>
+{
+    private static final String COMMAND_NAME = "purgedb";
+    private static final String COMMAND_DESCRIPTION = "Purge database";
+
+    public PurgeDatabaseCommand()
+    {
+        super(COMMAND_NAME, COMMAND_DESCRIPTION);
+    }
+
+    @Override
+    protected void run(Bootstrap<ApplicationConfiguration> bootstrap, Namespace namespace, ApplicationConfiguration applicationConfiguration) throws Exception
+    {
+        //todo: move and merge with app setup
+        Morphia morphia = new Morphia();
+        Datastore datastore = morphia.createDatastore(
+                new MongoClient(applicationConfiguration.getDbHost(), applicationConfiguration.getDbPort()), applicationConfiguration.getDbName());
+        datastore.getDB().dropDatabase();
+    }
+}