feat: Enable customizing the docker admin password (#29498)

docker/docker-init.sh

@@ -37,7 +37,7 @@ Init Step ${1}/${STEP_CNT} [${2}] -- ${3}
 
 EOF
 }
-ADMIN_PASSWORD="admin"
+ADMIN_PASSWORD="${ADMIN_PASSWORD:-admin}"
 # If Cypress run – overwrite the password for admin and export env variables
 if [ "$CYPRESS_CONFIG" == "true" ]; then
     ADMIN_PASSWORD="general"
@@ -57,7 +57,7 @@ superset fab create-admin \
               --firstname Superset \
               --lastname Admin \
               --email admin@superset.com \
-              --password $ADMIN_PASSWORD
+              --password "$ADMIN_PASSWORD"
 echo_step "2" "Complete" "Setting up admin user"
 # Create default roles and permissions
 echo_step "3" "Starting" "Setting up roles and perms"