Improve keycloak configuration docs

[forus]

• document url to download IDP SSO descriptor xml file.
• add complete logback xml file example to turn on DEBUG level
• document how to bind mount the logback xml file to docker container
• document what role name stands for when filter_groups_by_appname=false/true

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• Runs on heroku
• Has tests or has a separate issue that describes the types of test that should be created. If no test is included it should explicitly be mentioned in the PR why there is no test.
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• Is this PR adding logic based on one or more clinical attributes? If yes, please make sure validation for this attribute is also present in the data validation / data loading layers (in backend repo) and documented in File-Formats Clinical data section!

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[pieterlukasse]

Thanks @forus , this is a great improvement 👍

[sonarqubecloud]

Kudos, SonarCloud Quality Gate passed!   

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[dippindots]

@n1zea144 @jagnathan This seems a good improvement to our current keycloak documentation, could we get your review?

[inodb]

LGTM