[Fleet] Better default value for config kibana host and elasticsearch host

[nchaulet]

Description

Currently the default value for the default output hosts rely on xpack.ingestManager.elasticsearch.hosts (you can edit this in the UI after).

Let see if we can find a better default value, maybe from the kbn config elasticsearch.hosts.

Related to #64276

[jfsiii]

I spoke with @joshdover and he said

For elasticsearch.hosts there is a possible need to expose this to plugins. One known case is the Console application needs these configs. We currently expose this API to legacy, but not currently to NP plugins.

For Kibana’s server.host we don’t currently have a reliable way of knowing whether or not this is the public available hostname. There have been discussions about adding a publicAddress type configuration, but no decision moving forward on that yet.

So I think we'll have continue being creative

[jfsiii]

Pulling together a few Slack conversations:

There's a cloud Kibana plugin which exports isCloudEnabled and cloudId.

CloudId contains the ES and Kibana URLs.

We found this code which decodes it into the various parts https://github.com/elastic/beats/blob/master/libbeat/cloudid/cloudid.go

We'll duplicate the required parts inTS, then implement like "if cloud enabled and have cloud is, derive both URLs from cloud id. Otherwise, use xpack.ingestManager.* values. Otherwise use defaults".

@jfsiii will do the TS code and test/work with Cloud

[jfsiii]

Worked on this today. No time to push to draft yet, but if anyone needs to convert a CloudID string into the ES & Kibana URLs, this decodeCloudID should work. TS Playground link (click Run & look in console for passing tests)

I ported from https://github.com/elastic/beats/blob/master/libbeat/cloudid/cloudid.go & https://github.com/elastic/beats/blob/master/libbeat/cloudid/cloudid_test.go

I'll get up something more appropriate soon, but I just wanted to make this available for anyone currently waiting on it.