keycloak_user_federation: get the before mappers from `before_comp` to fix `UnboundLocalError` (#8831)
* fix: get the before mappers from `before_comp`
* add changelog fragment
* Adjust changelog fragment.
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Co-authored-by: Felix Fontein <felix@fontein.de>
(cherry picked from commit 2ae41fa83f)
Co-authored-by: fgruenbauer <gruenbauer@b1-systems.de>