Webhook endpoint: Handle doc expiration

[xmonader]

No description provided.

[sameh-farouk]

The feature is coded but blocked on https://github.com/threefoldtech/tf_operations/issues/2902 since I can't run the code and verify its functionality.

[xmonader]

Should go back to in progress

[sameh-farouk]

Update:
PR ready to review

[sameh-farouk]

Update:
The feature functions properly in environments where we have one instance per backend, such as in DevNet and QANet. However, in TestNet and MainNet, the document expiry notifications for clients on both networks are sent to only one instance, despite our attempts to override the callback URL during the creation of the verification session.

Idenfy's response:

After consulting with the technical team regarding the inquiry, it has been confirmed that the Document expiry notification will not be overwritten by callbackUrl. That parameter only impacts ID verification responses and events - auto and manual review, expiration, cancellation.

This handler needs to be revised, but it should not rely on webhooks anymore. see #24

[sameh-farouk]

Closed in favor of #24.