Add strict TOTP validation to block invalid authentication requests

[sharmagot]

This MR adds strict client-side validation for TOTP values in the Python driver to prevent invalid authentication requests from being sent to the server.

Problem

The Python driver currently allows invalid TOTP values (e.g., ot1234, opentext, values shorter/longer than 6 digits) to pass through and reach the server.
This results in unnecessary authentication attempts and inconsistent behavior.

Solution

Added explicit validation to ensure TOTP:

Contains only numeric characters (isdigit() check)

Is exactly 6 digits long

Added corresponding error messages and logger entries.

Applied validation both:

When TOTP is passed via connection options

When TOTP is entered interactively during authentication

Expected Behavior

Driver should block invalid TOTP values before sending an authentication request.

Only valid 6-digit numeric TOTP codes should be accepted.