* add optional fields to user
- this provides the back-end implementation for #2365
* fix mistakes in schema.rb
* renamed OptionalField to userOptionalField
* rename field column in user_optional_fields to label
* add uniqueness validation on user_optional_field labels
* scope flag uniqueness to user_id
* add indexing on label in user_optional_fields
* add optional fields to user
- this provides the back-end implementation for #2365
* fix mistakes in schema.rb
* add index on user_id for user_optional_fields
* Remove duplicate model
* Fix schema
* Re-add past indexes
* Remove old index
* Remove another old index
* add `null:false` to columns in optional fields
* add `null: false` to the migration
- Updated test to account for the null constraint
* add null:false to user_id on user_optional_tables
Co-authored-by: rhymes <rhymesete@gmail.com>
Co-authored-by: Ben Halpern <bendhalpern@gmail.com>
