[Feature Request] Add Stack Deployment Steps API Specs

[isivaselvan]

Use-cases

StackDeploymentSteps describes all the stack-deployment-steps related methods that the HCP Terraform API supports.

• List returns a list of deployment steps for a given deployment run.
• Read retrieves a single deployment step by its ID with optional related resources (e.g. stack-approval, stack-approval.user, stack-state.
• Advance advances a deployment step that is in the pending-operator state, unblocking the deployment from proceeding.
• Diagnostics lists the diagnostic messages (warnings/errors) reported for a deployment step.
• Artifacts retrieves a specific artifact for a deployment step — valid types are plan-description, apply-description, plan-debug-log and apply-debug-log

Attempted Solutions

None, currently not supported.

Proposal

Add support for Stack Deployment Steps as a new resource family in python-tfe.

• List Stack Deployment Steps
• Show a Stack Deployment Step
• List Stack Deployment Step Diagnostics
• Show a Stack Deployment Step Artifact
• Advance a Stack Deployment Step
• Add required models in src/pytfe/models/stack_deployment_step.py
• Add resource in src/pytfe/resources/stack_deployment_steps.py
• Update Client
• Add Examples under examples folder
• Add Unit tests in tests/units

All new code should follow existing project conventions:

• Pydantic v2 models with populate_by_name=True
• alias-based JSON:API field mapping
• _Service base class
• Iterator-based pagination via _list.