Users can not duplicate timesheet lines when they are not part of party admin group
When duplicating a timesheet line the users sees the following error: `You are not allowed to access "Timesheet Line"."Cost Price"` This is because this field is restricted to be read only by users of party admin group but [trytond reads all fields](https://foss.heptapod.net/tryton/tryton/-/blob/aad13f60163919501298be3f55495531f0598500/trytond/trytond/model/modelstorage.py#L444) before copying them which raises the error.
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