[Feature] Support option ssl.certificate_authorities for elasticstack_kibana_synthetics_monitor

[mag-mkorn]

Is your feature request related to a problem? Please describe.
I can not create http monitors using the elasticstack_kibana_synthetics_monitor resource with custom certificates.

Describe the resource you would like to have implemented.
The resource already targets the right API: https://www.elastic.co/guide/en/kibana/current/add-monitor-api.html

Describe the solution you'd like
The resource needs to implement an option for setting ssl.certificate_authorities, for example as ssl_certificate_authorities.

Describe alternatives you've considered
As of now, ssl_verification_mode must be set to none to check endpoints with custom certificates.

[biscout42]

Quick update here. Due-to elastic/kibana#187952 ssl.certificate_authorities is not supported in the provider yet (as many other ssl options).

We would need to plan the provider upgrade to 8.16 and synthetics fix to make it work.

@mag-mkorn , which kibana / ES stack version do you use?

[mag-mkorn]

We're currently still running 8.15.3. But upgrading to newer versions is no issue.

[biscout42]

I did prepare a change to support 8.16 in the provider #964 .

That will help to include certificate_authorities support.

While testing new kibana API version I faced the following (same described in the docs). API accepts ssl config option as documented in ssl support, but returns it key by key (not as a json object) in the response, here is an example:

   "ssl.certificate_authorities": [
      "ca1",
      "ca2"
   ],
   "ssl.certificate": "cert",
   "ssl.key": "key",
   "ssl.verification_mode": "full",
   "ssl.supported_protocols": [
      "TLSv1.0",
      "TLSv1.1",
      "TLSv1.2"
   ],

That forces me to support it in terraform provider key by key. I'm about to add support for following keys:

• certificate_authorities
• key
• certificate
• key_passphrase

Some fields are not supported by 8.16 synthetics yet, e.g.

Invalid monitor key(s) for http type: ssl.ca_sha256 | ssl.ca_trusted_fingerprint | ssl.cipher_suites | ssl.curve_types

@mag-mkorn , would that be enough for you to move forward?

[biscout42]

@mag-mkorn , after we release this one #967 certificate_authorities should work. Please, note, it requires stack version 8.16 and above.