feat: Pull cost attribution labels for tenant

[Pokom]

Following a similar path as limits to pull cost attribution labels for
tenants. Adds a new internal library cals/cals.go that provides an
interface that wraps the TenantProvider client. Updates all of the
wiring from Updated => Scraper to pass along the new cal client.

Starts the process of using the library in scraper.go, which right now
finds the cost attribution labels for a specific tenant. Returns an
empty slice if nothing is found.

This will be dependent upon the API changes being released to get cost
attribution labels defined at the tenant level.

My goal is to have a follow up PR that updates the telemeter bits to track executions by cost attribution labels.

• relies on https://github.com/grafana/synthetic-monitoring-api/pull/1750

[Copilot]

Pull Request Overview

This PR adds support for pulling cost attribution labels from tenant configuration. The implementation introduces a new cals package that wraps the TenantProvider client to fetch cost attribution labels at the tenant level, following a similar pattern to the existing limits functionality.

Key changes:

• New cals package with CostAttributionLabels client for fetching tenant-specific cost attribution labels
• Updated scraper to retrieve and log cost attribution labels during check execution
• Wiring changes throughout the codebase to pass the new CAL client from main through to scrapers

Reviewed Changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
internal/cals/cals.go	New package implementing TenantProvider wrapper for cost attribution labels
internal/cals/cals_test.go	Unit tests for the new cost attribution labels functionality
cmd/synthetic-monitoring-agent/main.go	Initializes and passes CAL client to the updater
internal/checks/checks.go	Wires CAL client through updater to scrapers
internal/checks/checks_test.go	Updates test scraper factory signature
internal/scraper/scraper.go	Integrates CAL client, retrieves and logs labels during scraping
internal/scraper/scraper_test.go	Adds test mock for CAL interface

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[The-9880]

Small nits, LGTM!

[The-9880]

You can use the interface here as well:

Suggested change

	costAttributionLabels *cals.CostAttributionLabels,
	costAttributionLabels TenantCals,

[The-9880]

You can use the interface here as well:

Suggested change

	cals *cals.CostAttributionLabels,
	cals TenantCals,

[The-9880]

If you're interested in a typed assertion here, you could define the following error in cals.go:

var (
    ErrTenantProvider := errors.New("fetching tenant data")
)

And update the CostAttributionLabels(...) method to wrap the tenant provider error:

if err != nil {
	return nil, fmt.Errorf("%w: %v", ErrTenantProvider, err)
}

Which you could assert for here like so:

if testcase.expectError {
	require.ErrorIs(t, err, TenantProviderError)
}