MAVEN user and password env variables won't get honored while downloading from mirror

Maven mirror URL is no longer public in customer's organization, it requires user/pass credentials to login

Customer have tried to use MAVEN_REPO_URL, MAVEN_REPO_USERNAME & MAVEN_REPO_PASSWORD variables inside the immutable-kieserver DC definition from template rhpam77-kieserver-externaldb but they doesn't appear in the output of `env` inside the container, just MAVEN_REPO_URL does.

Following variables were tried without luck.

MAVEN_MIRROR_URL
MAVEN_REPO_USERNAME
MAVEN_REPO_PASSWORD

MAVEN_REPO_URL
MAVEN_REPO_USERNAME
MAVEN_REPO_PASSWORD

MAVEN_MIRROR_URL
EXTERNAL_MAVEN_REPO_USERNAME
EXTERNAL_MAVEN_REPO_PASSWORD