[IMP] fields: remove support for non-string selections

[xmo-odoo]

Task https://www.odoo.com/web#id=1911598&model=project.task&menu_id=4720

[KangOl]

Do web client handle correctly the 0/1 selection fields with the boolean widget?

[rco-odoo]

@KangOl thanks for pointing that out, I haven't checked it.

[rco-odoo]

@KangOl I don't understand. IMHO, there is not point using the boolean widget with a selection field. The boolean widgets are aimed a boolean fields only.

We have used selection fields in place of boolean fields in the configuration wizard. The point was to use the radio button widget. This one works as expected.

[pedrobaeza]

@gurneyalex you had several reasons for using selection with integers instead of strings, do you?

[gurneyalex]

@pedrobaeza yes, interfacing with external systems which use enums. There are lots of these in the wild. The support was badly broken with "0" being not usable (displayed as unset, in Odoo), we ended up using stringified integers and adding int(val) and str(val) all over the place to parse / generate the expected values.

See for instance #11015

[rco-odoo]

@pedrobaeza @gurneyalex the purpose of this task is definitively to simplify things, and remove a feature that is both fragile and error-prone. See #28877 and #28891 for fixing such a terrible programming error.

[rco-odoo]

@KangOl are you okay with merging this?

[KangOl]

Yes.

[rco-odoo]

@robodoo r+

[robodoo]

Merged, thanks!