Allow an ID of object to be customized directly on the serializer by
passing a block to `set_id` as opposed to only through a model property.
We already allow for attributes that do not have a model property of the
same name to be customized directly on the serializer using a block.
This customization can be useful in situation in which you have
different classes being serialized using the same serializer. For
example, if we have `HorrorMovie`, `ComedyMovie` and `DramaMovie` using
the same `MovieSerializer`, we can unify their IDs using
```
class MovieSerializer
include FastJsonapi::ObjectSerializer
attributes :name, :year
set_id do |record|
"#{record.name.downcase}-#{record.id}"
end
```
which is preferable to creating a `#serialized_id` method in every model
that will use `MovieSerializer` to encapsulate the customization.
Closes#315
If you include a default empty `data` option in your JSON API response,
many frontend frameworks will ignore your `related` link that could be
used to load relationship records, and will instead treat the
relationship as empty.
This adds a `lazy_load_data` option which will:
* stop the serializer attempting to load the data and;
* exclude the `data` key from the final response
This allows you to lazy load a JSON API relationship.
Core extensions do not play well with many other gems; especially
considering that they only seem to be included for one `to_json` call,
they should be avoided.
If you forgot to set any `has_many` in the serializer and tried to serialize with an `include` you would get:
```
NoMethodError (undefined method `[]' for nil:NilClass):
```
That is not very helpful. Setting the variable with a default case makes sure the right error message gets displayed.
This allows specifying a `:links` option to a has_many/has_one
relationship, which means you can specify `self` or `related` links as
per the JSON API spec (these are often useful for not loading all
associated objects in a single payload)
