Export will fail when drawing new reaches

[ponceta]

Describe the bug
Create a new reach will make the export fails because they don't inherit yet of fk_dataowner and fk_provider which are mandatory for export.

To Reproduce
Exact steps to reproduce the behavior:

1. Create a new reach
2. Try to export
3. See error

Expected behavior¨
Drawing new reaches does not make the export fail.

Proposed solution
Make reach points inherit fk_dataowner and fk_provider from reaches (insert or update) so the export works without too much extra work.

Screenshots / data
If applicable, add screenshots or data to help explain your problem.

Desktop (please complete the following information):

• TWW version
• QGIS Version
• OS

Additional context
Add any other context about the problem here.

[cymed]

If digitised from the main reach view, we do set the values:

INSERT INTO tww_od.reach_point (
[...]
)
([...]
fk_dataowner = COALESCE(NULLIF(NEW.rp_to_fk_dataowner,''), NEW.fk_dataowner),
[...]
)

if NEW.fk_dataowner should have a default set from tww_od.default_values