The following constants were renamed:

  ActiveModel::Serialization     => ActiveModel::Serializable
  ActiveModel::Serializers::JSON => ActiveModel::Serializable::JSON
  ActiveModel::Serializers::Xml  => ActiveModel::Serializable::XML

The main motivation for such a change is that `ActiveModel::Serializers::JSON`
was not actually a serializer, but a module that when included allows the target to be serializable to JSON.

With such changes, we were able to clean up the namespace to add true serializers as the ArraySerializer.

This commit moves support for the :include serialization option for
serializing associated objects out of ActiveRecord in into ActiveModel.
The following methods support the :include option:

  * serializable_hash
  * to_json
  * to_xml

Instances must respond to methods named by the values of the :includes
array (or keys of the :includes hash). If an association method returns
an object that is_a?(Enumerable) (which AR has_many associations do), it
is assumed to be a collection association, and its elements must respond
to :serializable_hash. Otherwise it must respond to :serializable_hash
itself.

While here, fix #858, XmlSerializer should not singularize already
singular association names.

Attributes with :string type should not be given the type passed in model serialization options. Closes #1058

Signed-off-by: NJosé Valim <jose.valim@gmail.com>

Signed-off-by: NSantiago Pastorino <santiago@wyeworks.com>

Signed-off-by: NJosé Valim <jose.valim@gmail.com>

[#4529]
Signed-off-by: NJeremy Kemper <jeremy@bitsweat.net>

Move several configuration values from Hash to ActiveSupport::XmlMini, which both Hash and Array depends on.

Also, refactored ActiveModel serializers to just use ActiveSupport::XmlMini.to_tag. As consequence, if a serialized attribute is an array or a hash, it's not encoded as yaml, but as a hash or array.

Dasherize XML root by default to avoid invalid tags "<admin/posts>...</admin/posts>" [#2875 state:resolved]

Patch to ActiveModel's (and ActiveRecord, by association) XML serialization: If two parameters are present in Procs supplied to to_xml's :procs option, the model being serialized will be passed as the second argument [#2373 state:resolved]
Signed-off-by: NJoshua Peek <josh@joshpeek.com>