String Enum for Stage-Damage

[rnugent3]

We are going to have a stage-damage function for a damage category - damaged item category.

The damage categories are typically residential, commercial, industrial, and public. Other damage categories like emergency/clean-up costs and agriculture are less common but still relevant. The damaged items include structure, content, and other.

Do we want to develop something like a string enum with all the combinations to track all of the stage-damage functions?

[rnugent3]

@codymccoy suggest extending UPD to a StageDamage class that extends UPD