[On-prem Deployment - Managed DBs] attribute opensearch_domain_url is misleading

[mauroseb]

Describe the bug

The attribute named opensearch_domain_url makes the deployment fail when a URL pointing to OpenSearch is passed, but actually works with an FQDN (no schema specified).

To Reproduce

• Deploy an automate with an AWS managed OpenSearch instance: passing the attribute:
  opensearch_domain_url = "https://os.example.com"

• automate-es-gateway configuration will be generated incorrectly making nginx to bail out with the following error:

Jun 01 12:54:02 automate.example.com hab[684304]: automate-es-gateway.default(O): 2024/06/01 12:54:02 [emerg] 776785#0: invalid port in upstream "https:" in /hab/svc/automate-es-gateway/config/nginx.conf:33

Expected behavior

Deployment should succeed with a URL as the attribute name implies, or the attribute name should be changed to opensearch_fqdn or similar.

Versions:

• Automate Version 4.12.40

Additional context

The scenario to reproduce the issue is using on-prem deployment with AWS managed databases.