Make the Keycloak module usable in projects that require older Java versions.
Details
Currently the module requires at least Java 17.
dasniko/testcontainers/keycloak/KeycloakContainer has been compiled by a more recent version of the Java Runtime (class file version 61.0), this version of the Java Runtime only recognizes class file versions up to 55.0
Description
Consider supporting Java 11 or even Java 8.
Motivation
Make the Keycloak module usable in projects that require older Java versions.
Details
Currently the module requires at least Java 17.
Testcontainers seems to support Java 8. See https://github.com/testcontainers/testcontainers-java/blob/04206d9dff440e875906f01151f09ad04da3c68f/build.gradle#L39