Add a modal-triggering functionality when moving a card between columns in the Kanban board

[alvleont]

Overview

This proposal suggests extending the current Kanban board behavior to allow each column to define additional interactions when a card is moved into it. Currently, drag-and-drop updates only the position and status fields. Allowing columns to define optional modal schemas would make the board more flexible and better suited for real-world workflows.

Proposed Behavior

When a card is dragged from one column to another, the board could optionally trigger a modal containing a Filament form. The schema for this modal would be defined at the column level, enabling each column to request or modify specific data relevant to its status.

Example scenarios

• Moving a card to Completed could prompt the user to upload a required support file.
• Moving a card to In Progress could request an estimated completion date.
• Moving a card to Scheduled might allow editing priority or other planning details.

If a column does not define a schema, the existing behavior remains
unchanged.

Suggested API Direction

Columns could expose an optional schema() method (or similar) that
returns a Filament form schema. For example:

Column::make('completed')
    ->label('Completado')
    ->color('green')
    ->schema([
        FileUpload::make('support_file')->required(),
    ]);

If a schema is present:

1. When the card is dropped into that column, a modal is shown.
2. The modal displays the schema-defined form.
3. After submission, the data is saved to the model.
4. The card remains in the new column.

If the modal is canceled, the card could optionally revert to its
previous column.

Benefits

• Enables richer and more meaningful workflows in Kanban boards.
• Allows status transitions to gather required or contextual data.
• Provides a flexible and extensible mechanism that integrates
  naturally with Filament's form system.
• Improves expressiveness without altering the core board logic.

Optional Considerations

These are additional ideas that may enhance the implementation:

• Allow columns to define validation rules before allowing a move.
• Provide lifecycle hooks such as onMoveTo(Column $column).
• Support asynchronous saves after modal submission.
• Include a mechanism to revert card position on modal cancellation.

Summary

This feature would allow developers to attach optional modal schemas to Kanban columns, making the drag-and-drop process more interactive and aligned with real-world requirements.