[doc][skip ci] Add doc for DSN parser.

Author: makasim

docs/dsn.md

@@ -0,0 +1,77 @@
+## DSN Parser.
+
+The [enqueue/dsn](https://github.com/php-enqueue/dsn) tool helps to parse DSN\URI string. 
+The tool is used by Enqueue transports to parse DSNs. 
+
+## Installation
+
+```bash 
+composer req enqueue/dsn 0.9.x
+```
+
+### Examples
+
+Basic usage:
+
+```php
+<?php
+
+use Enqueue\Dsn\Dsn;
+
+$dsn = new Dsn('mysql+pdo://user:password@localhost:3306/database?connection_timeout=123');
+
+$dsn->getSchemeProtocol(); // 'mysql'
+$dsn->getScheme(); // 'mysql+pdo'
+$dsn->getSchemeExtensions(); // ['pdo']
+$dsn->getUser(); // 'user'
+$dsn->getPassword(); // 'password'
+$dsn->getHost(); // 'localhost'
+$dsn->getPort(); // 3306
+
+$dsn->getQueryString(); // 'connection_timeout=123'
+$dsn->getQuery(); // ['connection_timeout' => '123']
+$dsn->getQueryParameter('connection_timeout'); // '123'
+$dsn->getInt('connection_timeout'); // 123  
+```
+
+Some parts could be omitted:
+
+```php
+<?php
+use Enqueue\Dsn\Dsn;
+
+$dsn = new Dsn('sqs:?key=aKey&secret=aSecret&token=aToken');
+
+$dsn->getSchemeProtocol(); // 'sqs'
+$dsn->getScheme(); // 'sqs'
+$dsn->getSchemeExtensions(); // []
+$dsn->getUser(); // null
+$dsn->getPassword(); // null
+$dsn->getHost(); // null
+$dsn->getPort(); // null
+
+$dsn->getQueryParameter('key'); // 'aKey'
+$dsn->getQueryParameter('secret'); // 'aSecret'
+```
+
+Throws exception if DSN not valid:
+
+```php
+<?php
+use Enqueue\Dsn\Dsn;
+
+$dsn = new Dsn('foo'); // throws exception here
+```
+
+Throws exception if cannot cast query parameter:
+
+```php
+<?php
+use Enqueue\Dsn\Dsn;
+
+$dsn = new Dsn('mysql:?connection_timeout=notInt');
+
+$dsn->getInt('connection_timeout'); // throws exception here
+```
+
+[back to index](index.md)

docs/index.md

@@ -52,6 +52,7 @@
 * [Yii](#yii)
     - [AMQP Interop driver](yii/amqp_driver.md)
 * [EnqueueElasticaBundle. Overview](elastica-bundle/overview.md)
+* [DSN Parser](dsn.md)
 * [Use cases](#use-cases)
     - [Symfony. Async event dispatcher](async_event_dispatcher/quick_tour.md)
     - [Monolog. Send messages to message queue](monolog/send-messages-to-mq.md)