feat(pipelines): require shellIdentity on Shell steps in the schema (AROSLSRE-1380)

[raelga]

Problem

A Shell step's shellIdentity is effectively mandatory — sdp-pipelines EV2RA manifest generation validates it unconditionally and aborts if unset:

step ...: error validating step:
invalid shell identity: variable must specify config ref, value, or input chain

But shellStepBase in pipeline.schema.v1.json only marks command as required, so consumers that validate against the schema (e.g. ARO-HCP make validate-config-pipelines) without running EV2RA generation accept Shell steps that omit an identity. They only fail later, at bump time — which just caused an ARO-HCP revert/reland (Azure/ARO-HCP#5834 → #5888 / #5889).

What changes

Add shellIdentity to shellStepBase.required:

"required": [
  "command",
  "shellIdentity"
]

This also covers shellValidationStep, which embeds the same base. The Go type (shell.go) already documented the field as required. Existing valid-shell test fixtures are updated to declare shellIdentity.

Validation

• go test ./pipelines/types/... passes (schema + fixtures). The pipelines/graph failures in this environment are only missing graphviz/dot, unrelated to this change.

Follow-ups

• Un-hold once ARO-HCP is compliant (reland #5889 + hardening #5890).
• Optional: improve the runtime error to name the step and say shellIdentity is required.

[Copilot]

Pull request overview

This PR aligns the pipeline.schema.v1 JSON schema with existing runtime expectations by making shellIdentity required for all Shell steps, preventing configs from passing schema validation and only failing later during EV2RA manifest generation.

Changes:

• Updated shellStepBase.required in pipeline.schema.v1.json to include shellIdentity alongside command.
• Updated schema-validation unit tests to include shellIdentity in valid Shell step examples.
• Updated subscription provisioning schema validation tests to include shellIdentity in embedded Shell steps.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
pipelines/types/validation_test.go	Updates “valid shell” schema-validation test cases to include shellIdentity.
pipelines/types/pipeline.schema.v1.json	Makes shellIdentity a required property for Shell steps via shellStepBase.required.
pipelines/types/pipeline_test.go	Updates YAML test cases to include shellIdentity in Shell steps so they remain schema-compliant.

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