Insert cover only if a cover column is not null

[cymed]

At the moment, a new cover is created whenever a feature is created in vw_tww_wastewater_structure. As some ws have no cover (i.e. most discharge points and infiltration installations), we should only add a cover if any of the cover entries is distinct from NULL.

Edit:
This PR adds a meta function check_all_nulls, which allows to check whether all entries in a jsonb starting with a specific prefix are null. By default, the postfixes obj_id and identifier are ignored.

Example: tww_app.check_all_nulls(to_jsonb(NEW),'co') converts the record NEW to a jsonb. All fields starting with 'co_' are tested whether they are NULL except co_identifier and co_obj_id

The abovementioned meta function is now used to define whether a cover is added or not

[sjib]

Good idea, but I would give some user feedback, if no cover is added.

[urskaufmann]

good point, my solution in the pre-qgep-system was, that I could delete the cover when creating a wastewater_structure.
In qgep/tww we don't want the obj_id to be editable -> if we have a default value for identifier (= obj_id) then we can say, if the user delete the co_identifier, there will be no cover. One problem: I want co_identifier = ws_identifier as default. So the test, if there is a cover has to be before the identifier is set to ws_identifier...

[cymed]

I prefer an automated solution so I can use inserts on tww_app.vw_tww_wastewater_structure in gateway exports (i.E. from the Aargau models). Otherwise keeping the gateway up to date is tedious.

[cymed]

Good idea, but I would give some user feedback, if no cover is added.

I am now raising a warning.

[ponceta]

psql:/src/scripts/../changelogs/0001/09_tww_dictionaries.sql:122: NOTICE:  type "tww_od.plantype" does not exist, skipping
psql:/src/scripts/../app/14_geometry_functions.sql:34: NOTICE:  trigger "synchronize_level_with_altitude" for relation "tww_od.wastewater_node" does not exist, skipping
psql:/src/scripts/../app/14_geometry_functions.sql:76: NOTICE:  trigger "synchronize_level_with_altitude" for relation "tww_od.cover" does not exist, skipping
Traceback (most recent call last):
  File "/src/scripts/../app/view/create_views.py", line 273, in <module>
    create_views(
  File "/src/scripts/../app/view/create_views.py", line 193, in create_views
    vw_tww_wastewater_structure(
  File "/src/app/view/vw_tww_wastewater_structure.py", line 392, in vw_tww_wastewater_structure
    columns(
TypeError: columns() got an unexpected keyword argument 'indent'

[cymed]

This PR does not touch the plugin. Did we introduce an error somewhere else?

Edit: it now passes