Match current API endpoints (/links, /characters)
There is a pull request that is currently active (within the last day) for Active Model Serializers that will allow for nested and inline Serializers. This will allow `CardSerializer` to go from the complicated monstrosity that it is to a much simpler representation. For example
```
has_one :character
```
instead of:
```
def character
Api::V1::CharacterSerializer.new(object.character)
end
```
follow this pull request at https://github.com/rails-api/active_model_serializers/pull/1225
See merge request !1
