feat: allow configuration of step-up dialog

Description

feat: allow configuration of step-up dialog

• added 'step_up_available' option under 'mfa'
• when set to false, disable the step-up dialog and handle MFA exception as any other
• by default 'step_up_available' is set to true

DEPLOYMENT NOTE: new 'step_up_available' config option, set this to false to disable step-up dialog (e.g. when proxy doesn't support MFA)

How to test

Try an action that requires MFA (e.g. adding an attribute to your user object), modify instanceConfig.json and monitor the results.

Author's checklist

• I have followed the contribution guidelines
• This MR has been tested or does not change functionality
• I have added relevant merge request dependencies (if this MR has any)
• I have added the correct labels
• I have assigned reviewers (if any are relevant)
• I have edited the documentation (if the changes require it) or I have noted the need for the change if I do not have access to the documentation
• I have marked all introduced BREAKING CHANGES or necessary DEPLOYMENT NOTES in the commit message(s)

Reviewer's checklist

• This MR has been tested or does not change functionality
• This MR has correct commit message format

Other information

Also edited https://perunaai.atlassian.net/wiki/spaces/STRIBOG/pages/3440714/Configuration+of+new+GUI+applications to include the new property

Related issues

Closes STR-1206