[OJS 3.1.2] DOI Deposit cvc-pattern-valid error

Note: We needed to implement OJS 3 behind reverse proxy - how to achieve? - #10 by ctgraham for our SSL/HTTPS setup. Now we seem to run into the issue of relative links, see last comment here OJS 3 behind reverse proxy - how to achieve? - #17 by D_Schroeder_Micheel