Improve UFZ pipeline

Description

The first release of the SMS at UFZ showed that our pipeline is not as efficient as it should be.

• We've had problems creating images for stage and productive system (currently solved by a "hack").
• The pipelines got called very often (before and after every merge of a merge request).
• The pipelines took quite a long time ( 7 minute; 15 minute for releases)
• It should be possible to create images for the test (STAGE) system based either on develop or master branch for testing purposes This issue aims these problems and solution for these should be provided if possible.

Additional Feature:

• Pipeline Banner to Stage-System Job. Because the users try SMS also on Stage-System, it would be very helpfull, if a "This is the Testingsystem. If you use SMS in productive mode plese use SMS-Productive-System(link)." This Banner should be pop up if the user goes to the StageSystem-Landingpage and should be deactivated by a click to a cross.
• Also would be nice to use the DPVM-Stagesystem if the Stage-SMS-System is been builded (maybe make DPVM to an env-variable

Tasks

• Review current .gitlab-ci.yml
• Find the places that can be improved.
• Adjust the current behavior so that it is more efficient and resolves the aforementioned problems
• Document the deployment process

/cc @hannes.bohring @Normo