UFZ: add env for pid crednetials to dockerfile

Description

With release 1.16 the credentials PID_SERVICE_USER, PID_SERVICE_PASSWORD will be used. Even though they won't get set during the build process they should be available in the Dockerfiles for STAGE and PROD. They should be added similar to B2INST_TOKEN_ARG

Tasks

• Add PID_SERVICE_USER, PID_SERVICE_PASSWORD to STAGE Dockerfile
• Add PID_SERVICE_USER, PID_SERVICE_PASSWORD to PROD Dockerfile