M2 4786

[childmindhirsch]

Changes

This PR introduces the "None of the above" option for multi-select fields, which allows users to deselect other options when this is selected.

Implementation

• Added a new checkbox option with a special is_none_above property.
• Updated the session storage logic to retain the state of this option

[Damirkhon]

Hi @childmindhirsch, great to see you in the project.
I reviewed your changes, and have comments on the implementation:

1. You need to change the response_values models for MultiSelect, rather than config. Here you can see
   that _SingleSelectionValue is used for both singleselect and multiselect. But now, because we have difference between them we need to separate the models. Something like this:

class _MultiSelectionValue(_SingleSelectionValue, PublicModel):
    is_none_above: bool = Field(default=False)

And use it inside MultiSelectionValues class, probably like this:

class MultiSelectionValues(PublicModel):
    palette_name: str | None
    options: list[_MultiSelectionValue]
    
    @validator("options")
    def validate_options(cls, value):
        return validate_options_value(value)

2. Don't forget to implement another validation for it, that options inside MultiSelectionValues should not contain more than 1 option with is_none_above as true
3. Please, change current or add new unit and integration tests as well.

If you have any questions, feel free to contact via slack

[Damirkhon]

don't delete this config

[Damirkhon]

Re-implemented by #1089