feature: Add context object pattern (#2304)

* Add context object pattern and corresponding tests

* Update context pattern

* Add README, class diagram, puml file.
Add toString method in ServiceContext.java.
Add tests for coverage.

* Improvements:
Remove plugin in pom file
Add comments in app.java
Change local variable keyword to var in app.java
Use lombok for getters, setters and tostring
Change method signature in context object

* Refreshing environment-1

* Reconfigure pom file.

Co-authored-by: Alvis Chan <u7287079@edu.anu.au>
Co-authored-by: u7287079 <u7287079@anu.edu.au>