Update the RFC to use ActiveModelSerializers

After some internal discussion was decided to use the ActiveModelSerializers
namespace.

This patch update the content following this idea.

Ref:
https://github.com/rails-api/active_model_serializers/pull/1310/files#r45947587
https://github.com/rails-api/active_model_serializers/pull/1310/files#r47144210

Author: maurogeorge

docs/rfcs/0000-namespace.md

@@ -1,6 +1,6 @@
 - Start Date: (2015-10-29)
-- RFC PR: (leave this empty)
-- AMS Issue: (leave this empty)
+- RFC PR: https://github.com/rails-api/active_model_serializers/pull/1310
+- ActiveModelSerializers Issue: https://github.com/rails-api/active_model_serializers/issues/1298
 
 # Summary
 
@@ -25,91 +25,82 @@ At `ActiveModel` we have:
 
 - `ActiveModel::SerializableResource`
 
-The idea here is to provide a single namespace `ActiveModel::Serializers` to the user.
+The idea here is to provide a single namespace `ActiveModelSerializers` to the user.
 Following the same idea we have on other gems like
 [Devise](https://github.com/plataformatec/devise/blob/e9c82472ffe7c43a448945f77e034a0e47dde0bb/lib/devise.rb),
 [Refile](https://github.com/refile/refile/blob/6b24c293d044862dafbf1bfa4606672a64903aa2/lib/refile.rb) and
 [Active Job](https://github.com/rails/rails/blob/30bacc26f8f258b39e12f63fe52389a968d9c1ea/activejob/lib/active_job.rb)
 for example.
 
-# Detailed design
-
-## Require statement and main module
-
-We are adding a extension for the Active Model, so
-[following the Rubygens recomendation](http://guides.rubygems.org/name-your-gem/)
-for the gem name we need to change to this.
-
-|Gem name                  | Require statement          | Main class or module     |
-|--------------------------|----------------------------|--------------------------|
-| active_model_serializers | `active_model/serializers` | ActiveModel::Serializers |
-
-The expected gem name, in the gemspec is `active_model-serializers` but we don't
-need to change this, we can change the code without the need of a new gem on Rubygems.
-
-Active Model for example follow the same idea the gem name on gemspec is `activemodel` and to the end user is:
-
-|Gem name                  | Require statement          | Main class or module     |
-|--------------------------|----------------------------|--------------------------|
-| activemodel              | `active_model`             | ActiveModel              |
-
-As you can see we do not require `activemodel`(the gem name in gemspec) insted
-we use `active_model`.
+This way we are clarifing the boundaries of
+[ActiveModelSerializers and Rails](https://github.com/rails-api/active_model_serializers/blob/master/CHANGELOG.md#prehistory)
+and make clear that the `ActiveModel::Serializer` class is no longer the primary
+behavior of the ActiveModelSerializers.
 
-And based on the [bump of `0.10.0.pre` released by Steve Klabnik](https://github.com/rails-api/active_model_serializers/tree/86fc7d7227f3ce538fcb28c1e8c7069ce311f0e1)
-if we take a look on README and gemspec always is used `ActiveModel::Serializers`.
+# Detailed design
 
 ## New classes and modules organization
 
-Since this will be a big change we can do this on baby steps, read small PRs. A
+Since this will be a big change we can do this on baby steps, read small pull requests. A
 possible approach is:
 
-- Create the `ActiveModel::Serializers` namespace;
-- Move all content under `ActiveModelSerializers` to be under
-  `ActiveModel::Serializers`, the logger is on this step;
+- All new code will be in `lib/active_model_serializers/` using
+  the module namespace `ActiveModelSerializers`.
 - Move all content under `ActiveModel::Serializer` to be under
-  `ActiveModel::Serializers`, the adapter is on this steps;
-- Move all content under `ActiveModel` to be under `ActiveModel::Serializers`,
+  `ActiveModelSerializers`, the adapter is on this steps;
+- Move all content under `ActiveModel` to be under `ActiveModelSerializers`,
   the `SerializableResource` is on this step;
-- Now that all the code lives under `ActiveModel::Serializers` we can:
-  - create a better name to the `ActiveModel::Serializers::Serializer`
-    keeping in mind only to keep this in the same namespace
-  - create a better name to the `ActiveModel::Serializers::Serializer::Adapter::JsonApi`
-    probably remove this from the `ActiveModel::Serializers::Serializer`
-    and do something like `ActiveModel::Serializers::Adapter::JsonApi`
-    keeping in mind only to keep this in the same namespace
-  - Change all public API that doesn't make sense, keeping in mind only to keep
-    this in the same namespace
+- Change all public API that doesn't make sense, keeping in mind only to keep
+  this in the same namespace
 - Update the README;
 - Update the docs;
 
 The following table represents the current and the desired classes and modules
 at the first moment.
 
-| Current                                               | Desired                                          | Notes              |
-|-------------------------------------------------------|--------------------------------------------------|--------------------|
-|`ActiveModelSerializers` and `ActiveModel::Serializer` | `ActiveModel::Serializers`                       | The main namespace |
-| `ActiveModelSerializers.logger`                       | `ActiveModel::Serializers.logger`                ||
-|`ActiveModelSerializers::Model`                        | `ActiveModel::Serializers::Model`                ||
-|`ActiveModel::SerializableResource`                    | `ActiveModel::Serializers::SerializableResource` ||
-| `ActiveModel::Serializer`                             | `ActiveModel::Serializers::Serializer`           | I know that is probably a bad name, but In a second moment we can rename this to `Resource` [for example following this idea](https://github.com/rails-api/active_model_serializers/pull/1301/files#r42963185)|
-|`ActiveModel::Serializer.config`                       | `ActiveModel::Serializers.config`                ||
+| Current                                                | Desired                                          | Notes              |
+|--------------------------------------------------------|--------------------------------------------------|--------------------|
+| `ActiveModelSerializers` and `ActiveModel::Serializer` | `ActiveModelSerializers`                         | The main namespace |
+| `ActiveModelSerializers.logger`                        | `ActiveModelSerializers.logger`                  ||
+| `ActiveModelSerializers::Model`                        | `ActiveModelSerializers::Model`                  ||
+| `ActiveModel::SerializableResource`                    | `ActiveModelSerializers::SerializableResource`   ||
+| `ActiveModel::Serializer`                              | `ActiveModelSerializers::Serializer`             | The name can be discussed in a future pull request. For example, we can rename this to `Resource` [following this idea](https://github.com/rails-api/active_model_serializers/pull/1301/files#r42963185) more info about naming in the next section|
+| `ActiveModel::Serializer.config`                       | `ActiveModelSerializers.config`                ||
+
+## Renaming of class and modules
+
+When moving some content to the new namespace we can find some names that does
+not make much sense like `ActiveModelSerializers::Serializer::Adapter::JsonApi`.
+Discussion of renaming existing classes / modules and JsonApi objects will
+happen in separate pull requests, and issues, and in the google doc
+https://docs.google.com/document/d/1rcrJr0sVcazY2Opd_6Kmv1iIwuHbI84s1P_NzFn-05c/edit?usp=sharing
+
+Some of names already have a definition.
+
+- Adapters get their own namespace under ActiveModelSerializers. E.g
+  `ActiveModelSerializers::Adapter`
+- Serializers get their own namespace under ActiveModelSerializers. E.g
+  `ActiveModelSerializers::Serializer`
+
+## Keeping compatibility
+
+All moved classes or modules be aliased to their old name and location with
+deprecation warnings, such as
+[was done for CollectionSerializer](https://github.com/rails-api/active_model_serializers/pull/1251).
 
 # Drawbacks
 
-This will be a breaking change, so all users serializers will be broken.
-All PRs will need to rebase since the architeture will change a lot.
+This will be a breaking change, so all users serializers will be broken after a
+major bump.
+All pull requests will need to rebase since the architeture will change a lot.
 
 # Alternatives
 
 We can keep the way it is, and keep in mind to not add another namespace as a
 public API.
 
-Or we can start moving the small ones that seems to be the
-`ActiveModelSerializers` and `ActiveModel` and later we can handle the
-`ActiveModel::Serializer`.
-
 # Unresolved questions
 
 What is the better class name to be used to the class that will be inherited at
-the creation of a serializer.
+the creation of a serializer. This can be discussed in other RFC or directly via
+pull request.