Authentication

Branch: Authentication
Feature: Service API can only be accessed by a valid token which is generated by verifying the credentials.
Functions, and files which does the same are added.
strcmp() takes arguments of the type (const char*,const char *). resultPass is the hash of the password stored in the database retrieved in the string form. So converting this string to a const char* using c.str() function so that I could pass it to the strcmp() function somehow changes the hash. I don't know why there was this unexpected behavior cause the database was returning the correct string but c.str() ,apart from conversion, changes the character of the string as well. (It was not doing this for the username but only for the hash.)
That's why I implemented user defined strcmp() function.

I thought that == checks whether the memory location of the strings are same rather than equality of the strings. (I was uncertain about that).

Okay, now comparison is done using ==. And it works fine :)