Allow extra params in the dashboard auth request

[jraddaoui]

• Allow to configure and pass extra parameters in the dashboard OIDC authorization request.
• Rename enduro-secret to enduro-dashboard-secret and don't use it in the enduro manifest as the client id may differ from the one used in the dashboard.
• Trim all environment variables.
• Add documentation.

Refs #957.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 53.13%. Comparing base (82525cf) to head (27b772a). Report is 40 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #992 +/- ## ========================================== + Coverage 53.06% 53.13% +0.07% ========================================== Files 101 101 Lines 5661 5661 ========================================== + Hits 3004 3008 +4 + Misses 2408 2406 -2 + Partials 249 247 -2 ```

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