Unique constraint exception is not translated properly

[jpmoral]

When a unique constraint is violated the exception is translated as Statement Invalid. This is because the case statement in the translate_exception method doesn't handle the "violation of unique key constraint" message.
https://github.com/rails-sqlserver/activerecord-sqlserver-adapter/blob/master/lib/active_record/connection_adapters/sqlserver_adapter.rb#L390

[metaskills]

Closing this since there is a pull request.