**Steps to reproduce the problem**
- Define a contract template with one line with variable quantity and formula.
- Use that template in a new contract.
- Variable quantity type and formula are not transferred from template to contract.
This is due to the lack of that fields in the tree view that prevents web client to fetch
and store them.
We solve it adding those fields to the contract line tree view, also providing some
visibility logic for not showing the corresponding fields according the type.
No regression tests is provided, as this is only reproducible with web client, not through
code.
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Variable quantity in contract recurrent invoicing
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With this module, you will be able to define in recurring contracts some
lines with variable quantity according a provided formula.
Configuration
=============
* Go to Sales > Configuration > Contracts > Formulas (quantity).
* Define any formula based on Python code that stores at some moment a
float/integer value of the quantity to invoice in the variable 'result'.
You can use these variables to compute your formula:
* *env*: Environment variable for getting other models.
* *context*: Current context dictionary.
* *user*: Current user.
* *line*: Contract recurring invoice line that triggers this formula.
* *contract*: Contract whose line belongs to.
* *invoice*: Invoice (header) being created.
Usage
=====
To use this module, you need to:
* Go to Sales -> Contracts and select or create a new contract.
* Check *Generate recurring invoices automatically*.
* Add a new recurring invoicing line.
* Select "Variable quantity" in column "Qty. type".
* Select one of the possible formulas to use (previously created).
