User guide/channels guide

Channel guide with Magento integration details
You don't have to enumerate the list yourself, but you can relay on rst for this using the `#` character:

```rst
#. Go to Channels

#. `Define Basic Channel Details </user_guide/channel_guide.rst#2-define-basic-channel-details>`_

   a. `Define </user_guide/channel_guide.rst#2a-define-integration-details-for-a-magento-channel>`_  Integration
      details for a *Magento* Channel

#. `Fill the Channel with Entities </user_guide/channel_guide.rst#3-fill-the-channel-with-entities>`_

#. `Save the Channel in the System </user_guide/channel_guide.rst#4-save-the-channel-in-the-system>`_
```