feat: add internal user type management functions to IdentityManagerV2

[2PykeETH]

Summary

This PR introduces two new internal utility functions to IdentityManagerV2 that handle user tracking by type. These functions improve how the contract manages categorized users, ensuring consistent updates to internal mappings and arrays.

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Changes

• Added _addToUsersByType

  • Associates a user with a specific UserType
  • Tracks the user’s position in the usersByType array
  • Ensures efficient appending and retrieval

• Added _removeFromUsersByType

  • Removes a user from a UserType list while maintaining array compactness
  • Updates userPositions mapping for O(1) lookups
  • Cleans up state by deleting the user’s position record

• Natspec comments for both functions for improved readability and documentation.

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Benefits

• Provides modular internal helpers for managing users by type
• Ensures efficient array manipulation (swap-and-pop pattern)
• Simplifies logic for higher-level functions that depend on user categorization
• Improves maintainability with clear Natspec documentation

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Next Steps

• Integrate _addToUsersByType and _removeFromUsersByType into the verification and de-verification flows
• Add unit tests to confirm correct state management when users are added/removed across different types
• Extend stats tracking to leverage these helpers for more robust reporting

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Notes

These changes set the foundation for scalable identity management, where users may be grouped by type for permissions, analytics, or governance logic.