feat: export selection (GeoJSON, CSV, Excel) issue 49

[henkeberggren]

Summary

• Add export functionality to multiselect with a dedicated export modal (hidden by default for backward compatibility via showExportButton: false unless explicitly enabled).
• Support multiple export formats and configuration:
• GeoJSON
• CSV (optional WKT geometry column)
• Excel (attributes only, no WKT)
• Configurable allowed formats via exportFormats (defaults to all).
• Add property-selection UI in the export modal so users can choose which attributes to include in exports.
• Add configurable export filename base via exportFilename (extension added per format and filename sanitized).
• Add Excel export using xlsx and update bundling/import usage for the new dependency.
• Add modal-related styling updates (button classes and scrollable property list for large attribute sets).

Backward compatibility

• Export UI is opt-in (showExportButton defaults to disabled).
• Existing multiselect behavior remains unchanged unless export is enabled.

Configuration examples

• Enable export button:
  • showExportButton: true
• Restrict formats:
  • exportFormats: ['geojson', 'csv']
• Default filename base:
  • exportFilename: 'my-selection'
• CSV WKT default:
  • csvIncludeWkt: true

[asemoller]

This looks interesting.

I haven’t tested this yet, so I might be missing something obvious, but at a glance it seems somewhat similar to existing functionality in Origo. How does this differ?

Also, with this we would have multiple ways to export (since there are already several in Origo). Has that been considered from a user perspective, as it could potentially be confusing?

And was the existing functionality considered and a different approach chosen on purpose?

I might be completely off here since I haven’t tested this yet, I'm just curious to understand your reasoning.