RFC-0522 Ember-Data Deprecate default serializers and adapters (#436)

RFC-0522 Ember-Data Deprecate default serializers and adapters

content/ember-data/v3/default-adapter.md

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+---
+id: ember-data:default-adapter
+title: Default adapter usage
+until: '4.0.0'
+since: '3.12.0'
+---
+## Deprecates both store.defaultAdapter (which defaults to -json-api) and the -json-api adapter fallback behavior
+
+Previously, applications could define the store.adapter property which would be used by defaultAdapter and adapterFor as a fallback for when an adapter was not found by an exact name match.
+
+[RFC 522](https://github.com/emberjs/rfcs/pull/522) Deprecated specifying and using this property in favor of an explicit application adapter fallback.
+
+If you were not setting this value previously, the following should be sufficient to resolve this deprecation:
+
+create the file app/adapters/application.js with the following:
+
+```js
+    export { default } from '@ember-data/adapters/json-api';
+```
+
+
+If you were setting the adapter property previously to `<adapter-name>`, create the file app/adapters/application.js with the following:
+
+```js
+    export { default } from './<adapter-name>';
+```
+
+
+ More information about custom adapters can be found on the [ember.js/guides](https://guides.emberjs.com/release/models/customizing-adapters/) and in the [API DOCs](https://api.emberjs.com/ember-data/release/modules/@ember-data%2Fadapter)

content/ember-data/v3/default-serializer.md

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+---
+id: ember-data:default-serializers
+title: Default serializers usage
+until: '4.0.0'
+since: '3.12.0'
+---
+## Default serializer deprecations
+### deprecate adapter.defaultSerializer fallback
+Previously, if no application or type-specific serializer was specified, the store would attempt to lookup a serializer via the `defaultSerializer` property on the type's adapter. This behavior is deprecated in favor of explicitly defining a type-specific serializer or application serializer as described in "clearing these deprecations" below.
+
+### -default serializer fallback in store.serializerFor
+Previously, when no type-specific serializer, application serializer, or adapter defaultSerializer had been defined by the app, the `-default` serializer would be used which defaulted to `-json-api`. This behavior is deprecated in favor of explicitly defining an application or type-specific serializer as described below.
+
+## clearing these deprecations
+More information about custom serializers can be found in the [Serializer API Docs](https://api.emberjs.com/ember-data/release/modules/@ember-data%2Fserializer) or on the [ember.js/guides](https://guides.emberjs.com/release/models/customizing-serializers/#toc_customizing-serializers)
+
+If a specific model type requires custom serialization, a type-specific serializer can be created. A single `application` serializer can be used a for any model types not requiring custom serialization. To define a type-specific serializer, create an `app/serializers/[type].js` with the following:
+
+```js
+    import { JSONAPISerializer } from '@ember-data/serializers';
+
+    export default class UserSerializer extends JSONApiSerializer {
+      /*custom code*/
+    }
+```
+
+Defining a serializer for the entire application can be done by adding the file `app/serializers/application.js` with the following:
+
+```js
+    export { JSONAPISerializer } from '@ember-data/serializers';
+```
+
+
+
+

content/ember-data/v3/toJSON.md

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+---
+id: record.toJSON
+title: Record toJSON usage
+until: '4.0.0'
+since: '3.12.0'
+---
+## Deprecates the built in `record.toJSON`
+Previously users could use [`record.toJSON`](https://github.com/emberjs/data/blob/1be481a4924b2b4316c1cc151a58328c88903dcd/packages/store/addon/-private/system/model/model.js#L620) to get a simple JSON serialization of a record instance by either calling the method directly or using `JSON.stringify(record)`.
+
+This method used the now deprecated `-json` serializer to create this JSON representation of the record instead of the user supplied serializer. In addition to the surprising use of a different serializer, this creates an unnecessary dependency on the `JSONSerializer` for applications that may not otherwise have imported and uses this serializer.
+
+We have deprecated EmberData's own implementation of this method in favor of users implementing their own (or refactoring away).
+
+To clear this deprecation users may call record.serialize() or implement their own toJSON instead. The simplest 1:1 refactor is to import a serializer and define a `toJSON` method that returns the serialized data from the model, but users may want to consider implementing a custom "serialize" method that outputs relevant data.
+
+An example of the simple refactor is below:
+### before
+
+```js
+  //app/models/post.js
+  import Model from '@ember-data/model';
+
+  export default class Post extends Model {};
+
+  //other app code
+  const record = store.peekRecord('post');
+  // users the default serializer, will have a deprecation warning
+  const output = record.toJSON();
+```
+
+### after
+```js
+  //app/models/post.js
+  import Model from '@ember-data/model';
+  import { JSONAPISerializer } from '@ember-data/serializers';
+
+  export default class Post extends Model {
+    toJSON(options) {
+      /* Create a JSON object with relevant data by either:
+          - iterating the attributes / relationships of the record into a POJO
+          - calling this.serialize and then munge output into the desired shape
+      */
+    }
+  };
+
+  //other app code
+  const record = store.peekRecord('post');
+  // users the default serializer
+  const output = record.toJSON();
+```