Validate and monitor backends

[christophfriedrich]

In the long run, workarounds that were introduced to accommodate incompatible backends should be removed, as only fully spec-compliant backends should be listed in the Hub. See also this conversation.

Once possible, the following should be done:

• Remove check that tolerates non-existent links field in /collections (code)
• Expect HTTPS only (tolerating HTTP introduced in commit 66ceedd)
• Pass version number (from capabilities) to version prop of the components that are imported from openeo-vue-components (it's not passed so far because backends are under development and therefore their behaviour may differ from the API spec version they report they adhere to -> auto-detection yields better results)

list to be continued

[m-mohr]

Before removing the workarounds we need a way to validate the back-ends during crawling so we can ensure the stored data is valid and doesn't produce problems in the UI. Invalid back-ends need to be rejected (as if the server was not reachable) and the user be informed or at least it must be ensured that invalid back-end don't lead to errors in the Hub UI.

[christophfriedrich]

HTTPS is being enforced since a3b69b4 more than a year ago, this just had been tracked in a different issue, #59. If a URL doesn't start with https, the crawl script refuses it:

openeo-hub/crawl.js

Lines 76 to 77 in d5b06e3

	if(! url.startsWith('https')) {
	console.log("REFUSING to crawl insecure service " + serviceUrl + " that does not use HTTPS.\n");

openeo-hub/crawl.js

Lines 101 to 102 in d5b06e3

	if(! backendUrl.startsWith('https')) {
	console.log("REFUSING to crawl insecure backend " + backendUrl + " that does not use HTTPS.\n");

This works well as demonstrated by the current attempts to crawl https://openeo.creo.vito.be/.well-known/openeo.

The other two points from the list in the initial post refer to things that are not even part of the Hub code anymore (the Collection component) or have become obsolete over time (version props).

So from the workarounds perspective, this issue could be closed.

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But a proper validation of backends would still be good -- before enlisting, but also continuously to detect things like Open-EO/openeo-grassgis-driver#130. I don't reasonably see this in the Hub's scope for now, but we can keep it as an "idea that would be nice to have".