Changes for handling validations of rating

[vyomrastogi]

Changes include :

• Addition of @Validted and @Valid annotation in controller
• Test case to validate error message when rating is not present in request
• Additional handler in ExceptionHandler for handling validation scenario
• Refactor in service class to have common method to retrieve movie by title

@AmalesanS
I added some changes, feel free to take a look whenever you get time

PS: a lot of changes are showing up because of auto formatting

[AmalesanS]

@vyomrastogi Hi, I pulled the latest code and all the test cases are passing. I can also see you have completed the rest of the AC also. I like your commitment. If we had little more time, we could be able to complete this yesterday. I like your coding style and learnt a lot from you and am i sure, the experience will help me. Looking forward to pair program with you in the up-coming sessions.