Introduce WFS search

[dnlkoch]

This includes a generic WFS search option to the MultiSearch component while refactoring it to become no longer strongly linked to specific search engines.

To activate the search engine it's sufficient to add it to the engines array in the search config of the selected instance:

{
  "name": "search",
  "config": {
    "engines": [
      "nominatim",
      "wfs"
    ]
  }
}

For a searchable layer the existing configuration is untouched and supports solr and wfs the same way:

{
  "searchable": true,
  "searchConfig": {
    "attributes": [
      "NAME",
      "scalerank"
    ],
    "displayTemplate": "Result: {NAME}"
  }
}

Additional notes:

• this also suggests to removes the useNominatim option from the global application configurations since it's configurable by instance anyway.
• it's now possible to configure the nominatim server URL globally.
• the existing BasicNominatimSearch has been removed in favour of the refactored MultiSearch (having the same behaviour, but enables users to limit the search results to the given extent).

Please review @terrestris/devs.

[github-actions]

null

[dnlkoch]

Thanks for the review!

[github-actions]

🎉 This PR is included in version 9.0.0-next.3 🎉

The release is available on:

• npm package (@next dist-tag)
• GitHub release

Your semantic-release bot 📦🚀

[github-actions]

🎉 This PR is included in version 9.0.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot 📦🚀