Add rest-versioning.md to translate into Russian [skip ci]

docs/guide-ru/rest-versioning.md

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+Versioning
+==========
+
+Your APIs should be versioned. Unlike Web applications which you have full control on both client side and server side
+code, for APIs you usually do not have control of the client code that consumes the APIs. Therefore, backward
+compatibility (BC) of the APIs should be maintained whenever possible, and if some BC-breaking changes must be
+introduced to the APIs, you should bump up the version number. You may refer to [Semantic Versioning](http://semver.org/)
+for more information about designing the version numbers of your APIs.
+
+Regarding how to implement API versioning, a common practice is to embed the version number in the API URLs.
+For example, `http://example.com/v1/users` stands for `/users` API of version 1. Another method of API versioning
+which gains momentum recently is to put version numbers in the HTTP request headers, typically through the `Accept` header,
+like the following:
+
+```
+// via a parameter
+Accept: application/json; version=v1
+// via a vendor content type
+Accept: application/vnd.company.myapp-v1+json
+```
+
+Both methods have pros and cons, and there are a lot of debates about them. Below we describe a practical strategy
+of API versioning that is kind of a mix of these two methods:
+
+* Put each major version of API implementation in a separate module whose ID is the major version number (e.g. `v1`, `v2`).
+  Naturally, the API URLs will contain major version numbers.
+* Within each major version (and thus within the corresponding module), use the `Accept` HTTP request header
+  to determine the minor version number and write conditional code to respond to the minor versions accordingly.
+
+For each module serving a major version, it should include the resource classes and the controller classes
+serving for that specific version. To better separate code responsibility, you may keep a common set of
+base resource and controller classes, and subclass them in each individual version module. Within the subclasses,
+implement the concrete code such as `Model::fields()`.
+
+Your code may be organized like the following:
+
+```
+api/
+    common/
+        controllers/
+            UserController.php
+            PostController.php
+        models/
+            User.php
+            Post.php
+    modules/
+        v1/
+            controllers/
+                UserController.php
+                PostController.php
+            models/
+                User.php
+                Post.php
+        v2/
+            controllers/
+                UserController.php
+                PostController.php
+            models/
+                User.php
+                Post.php
+```
+
+Your application configuration would look like:
+
+```php
+return [
+    'modules' => [
+        'v1' => [
+            'basePath' => '@app/modules/v1',
+        ],
+        'v2' => [
+            'basePath' => '@app/modules/v2',
+        ],
+    ],
+    'components' => [
+        'urlManager' => [
+            'enablePrettyUrl' => true,
+            'enableStrictParsing' => true,
+            'showScriptName' => false,
+            'rules' => [
+                ['class' => 'yii\rest\UrlRule', 'controller' => ['v1/user', 'v1/post']],
+                ['class' => 'yii\rest\UrlRule', 'controller' => ['v2/user', 'v2/post']],
+            ],
+        ],
+    ],
+];
+```
+
+As a result, `http://example.com/v1/users` will return the list of users in version 1, while
+`http://example.com/v2/users` will return version 2 users.
+
+Using modules, code for different major versions can be well isolated. And it is still possible
+to reuse code across modules via common base classes and other shared classes.
+
+To deal with minor version numbers, you may take advantage of the content negotiation
+feature provided by the [[yii\filters\ContentNegotiator|contentNegotiator]] behavior. The `contentNegotiator`
+behavior will set the [[yii\web\Response::acceptParams]] property when it determines which
+content type to support.
+
+For example, if a request is sent with the HTTP header `Accept: application/json; version=v1`,
+after content negotiation, [[yii\web\Response::acceptParams]] will contain the value `['version' => 'v1']`.
+
+Based on the version information in `acceptParams`, you may write conditional code in places
+such as actions, resource classes, serializers, etc.
+
+Since minor versions require maintaining backward compatibility, hopefully there are not much
+version checks in your code. Otherwise, chances are that you may need to create a new major version.