x-pack/metricbeat/module/gcp: Override GCP API endpoint in metric client

[Linu-Elias]

Proposed commit message

The GCP metric client does not currently allow overriding with a custom endpoint, which is necessary for testing against a mock GCP API endpoint.
Resolved this issue by implementing a check to determine if an endpoint is specified in the GCP configuration, and subsequently overriding the ClientOption with that endpoint.

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

Author's Checklist

• [ ]

How to test this PR locally

Related issues

• Closes [GCP] Metricset metrics client allow overriding the endpoint #40848

Use cases

Screenshots

Logs

[mergify]

This pull request does not have a backport label.
If this is a bug or security fix, could you label this PR @Linu-Elias? 🙏.
For such, you'll need to label your PR with:

• The upcoming major version of the Elastic Stack
• The upcoming minor version of the Elastic Stack (if you're not pushing a breaking change)

To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• backport-8./d is the label to automatically backport to the 8./d branch. /d is the digit

[mergify]

backport-8.x has been added to help with the transition to the new branch 8.x.
If you don't need it please use backport-skip label and remove the backport-8.x label.

[elasticmachine]

Pinging @elastic/elastic-agent-data-plane (Team:Elastic-Agent-Data-Plane)

[pierrehilbert]

Approving for the data plane side as we are only owning the yml files.

[elasticmachine]

Pinging @elastic/obs-ds-hosted-services (Team:obs-ds-hosted-services)

[gpop63]

Let's keep a new line between these exported and unexported struct fields like it was before.

Suggested change

	Endpoint string `config:"endpoint"`
	opt []option.ClientOption
	period *durationpb.Duration
	organizationID string
	organizationName string
	projectName string
	Endpoint string `config:"endpoint"`
	opt []option.ClientOption
	period *durationpb.Duration
	organizationID string
	organizationName string
	projectName string

[gpop63]

Suggested change

	- Add `endpoint` field to the GCP configuration in order to append it to the metric client. {issue}40848[40848] {pull}40918[40918]
	- Add support for specifying a custom endpoint for GCP service clients. {issue}40848[40848] {pull}40918[40918]

[gpop63]

The yaml block is not properly formatted and it might be redundant to add it again just to showcase the endpoint config param. I would probably add endpoint to an existing config in that file.

[gpop63]

Add a new line to improve readability.

Suggested change

	if m.config.Endpoint != "" {
	m.Logger().Warnf("You are using a custom endpoint '%s' for the GCP API calls.", m.config.Endpoint)
	m.config.opt = append(m.config.opt, option.WithEndpoint(m.config.Endpoint))
	}
	if m.config.Endpoint != "" {
	m.Logger().Warnf("You are using a custom endpoint '%s' for the GCP API calls.", m.config.Endpoint)
	m.config.opt = append(m.config.opt, option.WithEndpoint(m.config.Endpoint))
	}