Simplify: references to avoid hardcoding and confusion

[harshadixit12]

Rather than hardcoding ID as "" and "[unknown]", refactoring to use constants, and functions for initialising the types. This will make the code more readable.

[Copilot]

Pull request overview

This PR refactors declarative planner/executor reference handling by replacing hardcoded sentinel strings ("", "[unknown]") with named constants and helper constructors/methods, to reduce ambiguity and improve readability across planning, dependency resolution, and execution.

Changes:

• Introduce RefIDPendingCreation / RefIDPendingLookup plus helper constructors and IsResolved/NeedsResolution methods for reference/parent IDs.
• Update planners and the reference resolver to use the new helpers instead of hardcoded sentinel strings.
• Update dependency resolution and executor logic/tests to use the new semantics consistently.

Reviewed changes

Copilot reviewed 16 out of 16 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
internal/declarative/planner/types.go	Adds reference/parent sentinel constants plus helper constructors and resolution methods.
internal/declarative/planner/resolver.go	Replaces "[unknown]" with RefIDPendingCreation in reference resolution.
internal/declarative/planner/portal_planner.go	Uses NewPendingLookupRef for portal auth-strategy references.
internal/declarative/planner/planner.go	Merges resolver results into existing ReferenceInfo while preserving lookup fields.
internal/declarative/planner/event_gateway_virtual_cluster_planner.go	Uses NewPendingLookupRef for gateway ID resolution.
internal/declarative/planner/event_gateway_tls_trust_bundle_planner.go	Uses NewPendingLookupRef for gateway ID resolution.
internal/declarative/planner/event_gateway_static_key_planner.go	Uses NewPendingLookupRef for gateway ID resolution.
internal/declarative/planner/event_gateway_schema_registry_planner.go	Uses NewPendingLookupRef for gateway ID resolution.
internal/declarative/planner/event_gateway_listener_planner.go	Uses NewPendingLookupRef for gateway ID resolution.
internal/declarative/planner/event_gateway_data_plane_certificate_planner.go	Uses NewPendingLookupRef for gateway ID resolution.
internal/declarative/planner/event_gateway_backend_cluster_planner.go	Uses NewPendingLookupRef for gateway ID resolution.
internal/declarative/planner/dependencies.go	Switches dependency checks to IsResolved/NeedsResolution helpers.
internal/declarative/planner/dependencies_test.go	Updates tests to use RefIDPendingCreation.
internal/declarative/executor/portal_operations_test.go	Updates executor portal test to use planner.RefIDPendingCreation.
internal/declarative/executor/executor.go	Centralizes unresolved-ID checks via constants and NeedsResolution/IsResolved.
internal/declarative/executor/executor_test.go	Updates executor tests to use planner.RefIDPendingCreation.

[rspurgeon]

@harshadixit12 please close or revive this PR when you are able.