Keep End-Client on the page they were at after TARA authentication (MVP)

[turnerrainer]

This issue is a clone of buerokratt/Chat-Widget#52 The scope of this issue is MVP version of Bürokratt

AS AN End-User I WANT TO stay on the same page after authenticating myself with TARA during an ongoing chat session SO THAT I COULD continue my chat after TARA authentication without interruptions

Acceptance Criteria

• [ ] The following AC applies to both new and ongoing chat sessions
• [ ] No changes in End-User authenticating via TARA regarding authentication flow
• [ ] After TARA authentication flow ends, End-User is redirected to the same page where they started their authentication

GUI

• [ ] When TARA authentication process is initiated, a cookie is set to indicate an incomplete authentication process
• [ ] Given cookie contains URL of where the process was initiated
• [ ] After successful TARA authentication process, End-Client is redirected to the URL extracted from the cookie
• [ ] After TARA authentication process has been finished, cookie is deleted

[turnerrainer]

Blocked until https://github.com/buerokratt/Buerokratt-Chatbot/issues/358 is finished