Additional use cases for abstraction patterns in mathlib

Identify other uses of the quotient-type representative abstraction pattern in mathlib to determine the appropriate formulation and namespace placement for a reusable generic version.

Background

The paper argues that the representative-selection definitions can be converted wholesale to a generic Quot-based formulation, demonstrating that the abstraction is feasible. However, the appropriate design depends on where analogous constructions occur throughout mathlib.

The unresolved issue is whether similar use cases exist beyond the current combinatorics application and, if so, whether the abstraction belongs in a combinatorics namespace or a more general Data namespace. The paper notes that locating such patterns in a very large codebase is non-trivial and suggests that search tools could assist.