# Functions
CookieParser return a one-time password parser, where otp extracted form HTTP Cookie.
JSONBodyParser return a one-time password parser, where otp extracted form request body.
QueryParser return a one-time password parser, where otp extracted form HTTP query string.
XHeaderParser return a one-time password parser, where otp extracted form "X-" header.
# Variables
ErrInvalidOTP is returned by twofactor strategy, When the user-supplied an invalid one time password and verification process failed.
ErrMissingOTP is returned by Parser, When one-time password missing or empty in HTTP request.