fix: use containeraddress for jwk-set-uri

[FritzHoing]

Description

Needs to be updated in shogun-docker also.

Related issues or pull requests

Pull request type

• Bugfix
• Feature
• Dependency updates
• Tests
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes
• Other (please describe)

Do you introduce a breaking change?

• Yes
• No

Checklist

• I understand and agree that the changes in this PR will be licensed under the
  Apache Licence Version 2.0.
• I have followed the guidelines for contributing.
• The proposed change fits to the content of the code of conduct.
• I have added or updated tests and documentation, and the test suite passes (run mvn test locally).
• I have added a screenshot/screencast to illustrate the visual output of my update.

[simonseyock]

This problem occurs if the KEYCLOAK_HOST is not reachable from inside the container.
The problem started to appear with the newest SHOGun version.
I noticed the same while using the helm-charts and opened this PR there: terrestris/helm-charts#90

[dnlkoch]

Not sure why this is needed, but removing the environment variable KEYCLOAK_HOST entirely seems not to be the right way to me.

[simonseyock]

The problem is that spring is accessing the jwk-set-uri to autoconfigure itself and retrieve some certificates from keycloak. If the KEYCLOAK_HOST is used, this only works if the KEYCLOAK_HOST is accessible from inside the container.

Using the container address and removing the KEYCLOAK_HOST here seems to be the solution, as this should be working in any environment.

The documentation is not exhaustive in that regard, but I understand it this way:

• The issuer-url is used to check the issuer field in the jwt. If jwk-set-uri is not set, this is also used to autoconfigure and retrieve the certificates.
• The jwk-set-uri is used instead for the requests if set

https://docs.spring.io/spring-security/reference/reactive/oauth2/resource-server/jwt.html#webflux-oauth2resourceserver-jwt-jwkseturi