Adjust lesson template (#704)

* Remove method `getId()` from all lessons as it defaults to the class name

* remove clean up endpoint

* remove unused class `RequestParameter`

* remove unused class `PluginLoadingFailure`

* Move `CourseConfiguration` to lesson package

* Add more content around the lesson template lesson and make it visible as a lesson in WebGoat

* Remove explicit invocation `trackProgress()` inside WebGoat framework so assignments only need to return an `AttackResult`

* Put original solution back as well for SQL string injection

* review comments

* Add

webgoat-lessons/webgoat-introduction/src/main/java/org/owasp/webgoat/introduction/WebGoatIntroduction.java

@@ -45,8 +45,4 @@ public class WebGoatIntroduction extends Lesson {
         return "webgoat.title";
     }
 
-    @Override
-    public String getId() {
-        return "WebGoatIntroduction";
-    }
 }