Add hidden_from_list field attribute

[Alwinator]

Summary

Adds a new hidden_from_list attribute to BaseField that allows hiding columns from the list view by default while still keeping them accessible via DataTables' Column Visibility button.

Motivation

Currently, the only way to remove a column from the list view is exclude_from_list, which completely removes the column from the DataTable — it cannot be toggled back by the user, and it is no longer available for filtering or searching.

There are cases where a field contains useful but non-essential information (e.g. long descriptions, internal IDs, timestamps) that should be hidden by default to reduce clutter, but still available for users who want to see it. Additionally, hidden fields can still be used for filtering and searching via Search Builder, which is valuable when users need to query on columns they don't need to see in every row.

hidden_from_list fills this gap: the column is rendered in the DataTable with visible: false via columnDefs, so users can reveal it using the Column Visibility button (enabled by default via column_visibility = True), and the column remains available for filtering and sorting.

Changes

starlette_admin/fields.py

• Added hidden_from_list: Optional[bool] = False attribute to BaseField dataclass.
• Added documentation for the new parameter.

starlette_admin/views.py

• Replaced direct pass-through of self.datatables_options in _configs() with a call to the new _merged_datatables_options() method.
• Added _merged_datatables_options(request) which deep-copies user-defined datatables_options, detects fields with hidden_from_list=True, and appends a columnDefs entry with {"visible": False, "targets": [...]} (offset by +1 to account for the leading checkbox column).

tests/test_base_model_view.py

• test_hidden_from_list_field_attribute — verifies the attribute defaults to False and can be set to True.
• test_hidden_from_list_still_in_field_list — confirms hidden fields are still included in get_fields_list (unlike exclude_from_list).
• test_hidden_from_list_excluded_field_not_in_list — confirms that exclude_from_list=True takes precedence and removes the field entirely.
• test_merged_datatables_options_hidden_columns — verifies correct columnDefs targets are generated for multiple hidden fields.
• test_merged_datatables_options_no_hidden — verifies no columnDefs are injected when there are no hidden fields.
• test_merged_datatables_options_preserves_user_options — verifies existing datatables_options keys are preserved.
• test_merged_datatables_options_merges_existing_column_defs — verifies the hidden column def is appended (not overwritten) when the user already has columnDefs.

Usage

class ArticleView(ModelView):
    fields = [
        IntegerField("id"),
        StringField("title"),
        TextAreaField("body", hidden_from_list=True),  # hidden by default, toggleable, filterable
        DateTimeField("created_at", hidden_from_list=True),
    ]

Backwards Compatibility

Fully backwards-compatible. hidden_from_list defaults to False, so existing views are unaffected. User-defined datatables_options (including existing columnDefs) are preserved and merged.