Proposed commit message

[Metricbeat] [Prometheus] Query dataset: make understandable error messages in case for http error codes

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in CHANGELOG.next.asciidoc or CHANGELOG-developer.next.asciidoc.

Disruptive User Impact

No impact

Author's Checklist

• [ ]

How to test this PR locally

My test environment:

• Metricbeat built locally
• Prometheus running in docker, configured to listen on HTTPS with local self-signed certs
• Cloud deployment of Elastic stack

Related issues

• Closes [Metricbeat] [Prometheus] Add proper error handling for query dataset when the auth/ssl is misconfigured #44446
• Relates [Prometheus]: Add username, password and SSL related fields for query dataset integrations#13751
• Relates [Prometheus] Add username, password, and SSL related fields for query dataset integrations#13969

Screenshots & Logs

When running Metricbeat with wrong Prometheus' username and password the error message looks like that now:

and the debug message to the logs

{"log.level":"debug","@timestamp":"2025-05-26T16:07:31.937+0300","log.logger":"prometheus.query","log.origin":{"function":"github.com/elastic/beats/v7/metricbeat/module/prometheus/query.(*MetricSet).Fetch","file.name":"query/query.go","file.line":101},"message":"error received from prometheus endpoint: Unauthorized\n","service.name":"metricbeat","ecs.version":"1.6.0"}

When the protocol is HTTP but the Prometheus is configured to use HTTPS:

and the debug message to the logs:

{"log.level":"debug","@timestamp":"2025-05-26T16:06:09.560+0300","log.logger":"prometheus.query","log.origin":{"function":"github.com/elastic/beats/v7/metricbeat/module/prometheus/query.(*MetricSet).Fetch","file.name":"query/query.go","file.line":101},"message":"error received from prometheus endpoint: Client sent an HTTP request to an HTTPS server.\n","service.name":"metricbeat","ecs.version":"1.6.0"}

Which is now the same behavior as of collector submodule