Datahub: Propose external viewer button for geojson files

[tkohr]

The PR proposes the external viewer button for geojson files as seen on the screenshot.

Can be tested on http://localhost:4200/dataset/accroche_velos with the following config:

geonetwork4_api_url = "https://mel.integration.apps.gs-fr-prod.camptocamp.com/geonetwork/srv/api"
proxy_path = "/dev-proxy?"
external_viewer_url_template = 'https://mel.integration.apps.gs-fr-prod.camptocamp.com/mapstore/#/?actions=[{"type":"CATALOG:ADD_LAYERS_FROM_CATALOGS","layers":["${layer_name}"],"sources":[{"url":"${service_url}","type":"${service_type}"}]}]'

Note that the deployed mapstore version needs to support this feature and the link url indicated in the metadata for the geojson file needs to allow CORS requests.

[github-actions]

Affected libs: feature-record, feature-router, util-app-config, feature-map, feature-dataviz,
Affected apps: metadata-editor, datahub, demo, webcomponents, search, map-viewer,

• 🚀 Build and deploy storybook and demo on GitHub Pages
• 📦 Build and push affected docker images

[coveralls]

coverage: 86.302% (+4.4%) from 81.942%
when pulling 387b474 on external-geojson
into 19be416 on main.

[fgravin]

Excellent, thanks for adding those tests.
I've tested it and it works well !