Missing relation widget fk_massnahme in form Maintenance_event

[sjib]

Describe the bug
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In the form the fk_measure does not allow to select an existing measure

To Reproduce
Exact steps to reproduce the behavior:

1. Go to Tab 'Maintenance_Event'
2. Click on 'Add'
3. Scroll down to 'fk_measure'
4. See that there is no value list available

Expected behavior
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As in other attributes (fk_dataowner etc.) measure should be selectable

Screenshots / data
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Desktop (please complete the following information):

• TWW version 2024.0.3
• QGIS Version 3.34.8
• OS win 10

Additional context
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