#165368514 Implement LFA feedback on returning appropriate status codes from API's

[tolulope-od]

What does this PR do?

Refactors controllers to return the appropriate HTTP responses for new transactions and error handling

Description of Task to be completed?

• Return appropriate error code when a user is not found
• Return appropriate error code when a new transaction (debit or credit) is carried out
• Fix implicit return error on authorization middleware and return the appropriate response code

How should this be manually tested?

After cloning the repo, cd into it and do the following:

# install dependencies
npm install

# run unit tests
npm test

Using Postman:
Visit the sign in route created in #29 at localhost:5000/api/v1/auth/signin without registering. This should return an error with a status code of 404

Any background context you want to provide?

N/a

What are the relevant pivotal tracker stories?

#165368514

Screenshots (if appropriate)

[coveralls]

Coverage increased (+0.02%) to 96.305% when pulling 9ca4760 on ch-implement-status-codes-feedback-165368514 into b34e41b on develop.

[coveralls]

Coverage increased (+0.02%) to 96.305% when pulling 9ca4760 on ch-implement-status-codes-feedback-165368514 into b34e41b on develop.