this method is starting to get a little hard to understand.

What do you think about changing `attribute` to `attribute_name`, and splitting it into two methods for a lil extra clarity?

```ruby
def find_by_existing_record_params
  Array(options[:find_existing_by])
end

def find_by_existing_record_criteria
  find_by_existing_record_params.inject({}) do |params, attribute_name|
    params.merge! { attribute_name => attributes.find_by_name(attribute_name).value }
  end
end
```