Refactor zoning district class category from enum to check constraint

[TangoYankee]

Acceptance criteria

• Remove the categoryEnum from zoning-district-class
• Change the category field from a categoryEnum to a text type
• Add a check constraint to the category field which ensures the value is one of the options previously enforced by the enum
  • Note: the zoningDistrictClassCategoryEntitySchema should remain untouched. We are still using the field like an enum in the javascript api.
• Generate a drizzle migration

Related

Depends on #386