Feature/os interface

This MR updates the structure and adds content and info for the managing network interface page.

• TODO: add GUI detaching
• TODO: fix howto link (moved)

topics/compute/openstack/docs/how-to-guides/attaching-interface.md

----
-
-title: Attaching Network Interface
-search:
-  exclude: false
----
-
-# Attaching Network Interface
-
-## Prerequisites
-
-- Created [instance](../getting-started/creating-first-infrastructure.md).
-
-## Attaching Interface
-
-This guide shows how to attach additional interfaces to running instances. This approach can be used for both IPv4 and IPv6 networks.
-
-!!! info
-
-    If you approach a problem with your IPv6 deployment, please refer to [IPv6 troubleshooting](../additional-information/ipv6-troubleshooting.md).
-
-=== "GUI"
-
-    Go to **Project > Compute >  Instances**. Click on the menu **Actions** on the instance you wish to change and click on **Attach interface**.
-
-    !!! example
-
-        ![](/compute/openstack/images/networks/attach_interface.png)
-
-    In the **Network** dropdown menu select available IPv6 network.
-
-    !!! example
-
-        ![](/compute/openstack/images/networks/ipv6_attach.png)
-
-=== "CLI"
-
-    **Get ID of your VM, in this instance named my-vm**
-
-    ```
-    VM_ID=$(openstack server list --name my-vm -f value -c ID)
-    ```
-
-    **Create port for the network**
-
-    ```
-    openstack port create --network public-muni-v6-432 --security-group default --host ${VM_ID} ipv6-port
-    ```
-
-    Additional port configuration is available in [official CLI documentation](https://docs.openstack.org/python-openstackclient/train/cli/command-objects/port.html).