feat(jans-auth-server): introduce per tab session support for AS (via tab_id)

[yuriyz]

Description

Lets say we have scenario:

1. user1 logs in -> session1 is created
2. user2 hits authorization endpoint with prompt=select_account and gets logged in -> session2 is created.

session_id: de510ab6-b06c-4393-86d8-12a7c501aafe
current_sessions: ["de510ab6-b06c-4393-86d8-12a7c501aafe", "c691e83d-eb1b-41f0-b453-fab905681b5b"]

Only one session is active and in above scenario it will be user2.

Goal is to support in each tab own session. So end-user can have tab1 opened with user1 and tab2 with user2.

Possible solution:
We can introduce lets say tab_id and then SSO will work as combination of session_id and tab_id. tab_id is explicit request parameter and it will be stored in browser’s sessionStorage which is tab specific. So we need proper coding on front-channel pages and proper handling on AS endpoints. If tab_id is absent it will work as today (based on session_id cookie).

Test cases and code coverage

• Write unit test to cover added/changed code
• Update integration tests to cover added/changed code
• documentation