#11: started adding descriptive text for automatic openapi documentation (especially for use documenting metadata)

#3: found solution for loading controlled vocabulary only once at start time (with raw database connection); have to put it into place (so that pytests are also running); for now the workaround is still active

#4: nested download for station inside timeseries still not working properly, but at least shows some information; upload after gitlab crash

#4: nested download was extended for timeseries; TBD: showing nested station information is not working yet; also changed programme from many-to-many to 1:n

#3: added unique constraint to controlled vocabularies; added foreign keys (controlled vocabularies) to models

#3,#4: nested uploads/downloads using controlled vocabulary; still to investigate: how to load enum_tables at beginning (this commit is a workaround)

#3: now nested human readable download is established for timeseries; TBD: do this for all other modesl

#3: toar_controlled_vocabulary is used for downloading timeseries, pytests are added for timeseries; not yet working: how to show human readable fields inside nested models (how is this 'conversion' done automatically?)