Add service class to trigger external control

What does this MR do and why?

1. Add service class to trigger external compliance requirement controls
2. The corresponding project's project_control_compliance_statuses would be marked as "pending".
3. Currently, this service class is not being invoked any where in the code, however, in upcoming MRs we would be using this service class from a worker.

References

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How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. Ensure you have ultimate license.
2. For verification you need to create a compliance framework.
3. You would also need to create at least one compliance requirement for this framework using the GraphQL API.
4. You would also need to create at least one external control for the above compliance requirement. We do not support GraphQL API for this so you can use rails console for now.

cr = ComplianceManagement::ComplianceFramework::ComplianceRequirement.last
cr.compliance_requirements_controls.create!(control_type: 'external', name: "external_control", namespace_id: cr.namespace_id, external_url: "https://huzaifaiftikhar.requestcatcher.com", secret_token: "SECRET")

5. Since this service is not exposed via an API or UI, we would need to use rails console for validation.

project = Project.find(20) # or any other existing project ID

framework = ComplianceManagement::Framework.last

cr = framework.compliance_requirements.last

control = cr.compliance_requirements_controls.last

ComplianceManagement::ComplianceFramework::ComplianceRequirements::TriggerExternalControlService.new(project, control).execute

6. Ensure that the service returns a successful response and also the status of control in project_control_compliance_statuses is updated to 'pending'.

Closes #513421 (closed)