Customizable acceptedFileTypes in ImportAction

[locshino]

[Feature Request]: Customizable acceptedFileTypes in ImportAction

Is your feature request related to a problem? Please describe.

Currently, in Filament\Actions\ImportAction, the acceptedFileTypes for the FileUpload component are hardcoded within the setUp() method:

->acceptedFileTypes(['text/csv', 'text/x-csv', 'application/csv', 'application/x-csv', 'text/comma-separated-values', 'text/x-comma-separated-values', 'text/plain', 'application/vnd.ms-excel'])

This prevents developers from easily overriding or extending the allowed MIME types for the CSV import. For example, some systems, browsers, or operating systems might identify CSV files with slightly different or obscure MIME types, and developers cannot add them without entirely overriding the $action->schema([...]), which is very cumbersome as it requires duplicating the internal CSV parsing logic present in the original setUp() method.

Describe the solution you'd like

It would be extremely helpful to introduce a property and setter/getter methods for acceptedFileTypes within the ImportAction class so it can be customized fluently.

Example implementation:

protected array | Closure $acceptedFileTypes = [
    'text/csv',
    'text/x-csv',
    'application/csv',
    'application/x-csv',
    'text/comma-separated-values',
    'text/x-comma-separated-values',
    'text/plain',
    'application/vnd.ms-excel'
];

public function acceptedFileTypes(array | Closure $types): static
{
    $this->acceptedFileTypes = $types;

    return $this;
}

public function getAcceptedFileTypes(): array
{
    return $this->evaluate($this->acceptedFileTypes);
}

Then, in the setUp() method, simply call it dynamically:

FileUpload::make('file')
    // ...
    ->acceptedFileTypes($action->getAcceptedFileTypes())

This allows developers to do:

ImportAction::make()
    ->importer(UserImporter::class)
    ->acceptedFileTypes([
        // custom types
    ]);

Describe alternatives you've considered

1. Overriding the schema(): We can call ->schema([...]) on the ImportAction, but this involves copying a massive chunk of logic handling the CSV chunking and parsing directly into the resource file, which defeats the purpose of having a pre-built action.
2. Subclassing ImportAction: We can create a custom CustomImportAction extends ImportAction and override setUp(). However, this again requires copying the entire setup block just to change one line of code (->acceptedFileTypes([...])).

Additional context

Providing a way to customize acceptedFileTypes is consistent with how other properties are handled in Filament actions (e.g., chunkSize, maxRows, csvDelimiter, etc. all have their own setter methods).