API support for tagged device attachment

This patch adds microversion 2.49, which supports tagged attachment
of network interfaces and block devices.

Change-Id: I8d3bbe7e9a21d2694d10ee89628deb333e6b0487
Implements: blueprint virt-device-tagged-attach-detach

api-ref/source/os-interface.inc

@@ -71,6 +71,7 @@ Request
   - net_id: net_id
   - fixed_ips: fixed_ips
   - ip_address: ip_address_req
+  - tag: device_tag_nic_attachment
 
 **Example Create Interface: JSON request**
 
@@ -84,6 +85,11 @@ Create interface with ``port_id``.
 .. literalinclude:: ../../doc/api_samples/os-attach-interfaces/attach-interfaces-create-req.json
    :language: javascript
 
+**Example Create Tagged Interface (v2.49): JSON request**
+
+.. literalinclude:: ../../doc/api_samples/os-attach-interfaces/v2.49/attach-interfaces-create-req.json
+   :language: javascript
+
 Response
 --------