If the `id` attribute for a class isn't taken directly from the object when
serializing it, it may be desirible for other classes that serialize a
relationship with that class to overwrite the relationship IDs they serialize.
For example, suppose we have:
```(ruby)
class Repo < Model
attributes :id, :github_id, :name
associations :configs
end
class Config < Model
attributes :id
belongs_to :repo
end
class RepoSerializer < ActiveModel::Serializer
attributes :id, :name
has_many :update_configs
def id
object.github_id
end
end
class ConfigSerializer < ActiveModel::Serializer
attributes :id
belongs_to :repo
end
```
In the above example, serializing a list of `Repo`s will give the `github_id`
for each one, but serializing a `Config` will give the `id` for its parent repo.
Ideally AMS would inspect the `RepoSerializer` when serializing the `Config`,
and realise it can't just output the foreign key. Unfortunately, getting the
serialization class for the child repo currently requires loading the record
(via evaluating `lazy_assocation`), and loses the performance benefit of the
existing `belongs_to?` path. Instead, I've opted to use
`read_attribute_for_serialization` instead of `object.send` to fetch the
serialized foreign key. This allows the serialized relationship ID to be
overwritten using
```(ruby)
class ConfigSerializer < ActiveModel::Serializer
...
def repo_id
object.repo.github_id
end
end
```
Also, fix test where attributes were included when id was ""
```
1) Failure:
ActionController::Serialization::AdapterSelectorTest#test_render_using_adapter_override
[test/action_c$ntroller/adapter_selector_test.rb:53]:
--- expected
+++ actual
@@ -1 +1 @@
-"{\"data\":{\"id\":\"\",\"type\":\"profiles\",\"attributes\":{\"name\":\"Name 1\",\"description\":\"Description 1\"}}}"
+"{\"data\":null}"
```
- Updating general/serializers.md
- Updating docs/general/rendering.md
- adding to changelog
- Updating rendering.md to indicate that `each_serializer` must be used on a collection
- updating my handle in previous changelog entry
