E1464. Refactoring User model

Refactored code for User Model where we made the following changes:

* Inefficient boolean logic present at multiple lines in the code
* Not using [ ] & { } instead of Array.new & Hash.new (for reasons like code hygiene and efficiency)
* Using “key => value” instead of “key: value”
* Not using in-built array functions such as one?, any?, zero?, first & last 
* Methods that were not being used
* Methods that were just delegating their implementations to other functions in other classes