Test cases for logout api and fixed http status code for isValidSession Middleware

[aditya-garg-09-01-2002]

• Required To publish the logout api after adding tests.

Closes Issue Ref #14

• Created a new file for writing tests for logout api
• Created the following tests
  • Logout from session when valid session jwt and cookie are present
  • Logout failure for absent/missing session jwt/cookie
  • Logout failure for invalid session jwt/cookie.