[Documentation] Add differnt ways of using keycloak security

[DanielOber]

Relevant documentation

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Problem description (optional)

The Keycloak and Spring security can be used in different ways, depending on what is needed. We need to document the different ways

Desired solution

add the following concepts to the documentation for keycloak security:

• roles
• use-case roles
• application roles

Additional context (optional)

• Internal discussion: https://git.muenchen.de/ccse/Architekt_innenrunde/-/issues/161

No duplicate

• I confirm that this issue is not a duplicate

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• I agree to follow this project's Code of Conduct

[devtobi]

Also relevant: it-at-m/refarch-templates#200

[eidottermihi]

probably also relevant: it-at-m/refarch-templates#191