Renamed class files

Signed-off-by: Shivam Dixit <shivamd001@gmail.com>
Removed redundant file

Signed-off-by: Shivam Dixit <shivamd001@gmail.com>
Converted indents to spaces

Signed-off-by: Shivam Dixit <shivamd001@gmail.com>
Renamed exceptions as per new exceptions class

Signed-off-by: Shivam Dixit <shivamd001@gmail.com>
Added function to get challenge detail by contest id

Signed-off-by: Shivam Dixit <shivamd001@gmail.com>
Added condition if contest is present

Signed-off-by: Shivam Dixit <shivamd001@gmail.com>