Information accessible through `phlex::handle<T>`

[knoepfel]

Discussed in https://github.com/orgs/Framework-R-D/discussions/63

^{Originally posted by knoepfel October 23, 2025 at https://github.com/orgs/Framework-R-D/discussions/63#discussioncomment-14773665}
Users will have programmatic access to data-product provenance through a Phlex handle. The behaviors of and information available through a handle need to be discussed.

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The comment specifically mentions that the following should be accessible through a data-product handle:

• The data product itself
• The index of the data cell to which the data product belongs
  • This is not a single number; it would be a tuple of identifiers like: (run: 4, subrun: 8, spill: 15)
• The data-product concept modeled by the concrete data-product type
• The creator name, which includes:
  1. the algorithm name
  2. the name of the module in which the algorithm was registered
• The product suffix
  • A user is not always required to provide a product suffix—the product suffix is used to disambiguate between multiple products of the same type returned by the same algorithm invocation.
  • This term replaces the term product name, although the latter will be explored further.
• The phase name (or stage name)

[knoepfel]

The data product concept may not be able to be provided in time for Prototype 0.2. If that's the case, then the scope of this issue should focus on just the product suffix, the creator name, and the phase name, and a separate issue should be created regarding providing access to the data-product concept.