Discuss whether data_product_concept::name_ should use phlex::identifier #1040

Summary

Discuss whether phlex::experimental::data_product_concept::name_ should use phlex::identifier instead of std::string const.

The current declaration stores an immutable string name. The name must remain consistent with the concept registry key. This issue requests a design decision, not an immediate type change.

Discussion scope

• Compare the semantics of phlex::identifier with the requirements for concept names, including validation, equality, ordering, and conversion to display text.
• Evaluate the effect on the constructor, name() accessor, and registry keys and lookup APIs.
• Preserve the invariant that a registered concept's name cannot change independently of its registry key.
• Determine whether consistency with other model identifiers justifies a change and identify any API compatibility implications.

Affected areas

• phlex/model/data_product_concept.hpp
• phlex/model/data_product_concept.cpp
• phlex/model/identifier.hpp
• phlex/model/data_product_concept_registry.hpp
• phlex/model/data_product_concept_registry.cpp
• Associated concept and registry tests, if a change is selected.

Completion criteria

• Record a decision to retain the string name or adopt phlex::identifier, with rationale.
• If a change is selected, define the required API, registry, and test updates as follow-up work.

Context

Requested by @knoepfel.

• PR: feat(model): add data product concept and registry #1001
• Review discussion: feat(model): add data product concept and registry #1001 (comment)