libvirt: allow direct SPICE connections to qemu

This patch adds a new console type, "spice-direct", which provides
the connection information required to talk the native SPICE protocol
directly to qemu on the hypervisor. This is intended to be fronted
by a proxy which will handle authentication separately.

A new microversion is introduced which adds the type "spice-direct"
to the existing "spice" protocol.

An example request:

POST /servers/<uuid>/remote-consoles
{
  "remote_console": {
    "protocol": "spice",
    "type": "spice-direct"
  }
}

An example response:

{
  "remote_console": {
    "protocol": "spice",
    "type": "spice-direct",
    "url": "http://localhost:13200/nova?token=XXX";
  }
}

This token can then be used to lookup connection details for the
console using a request like this:

GET /os-console-auth-tokens/<consoletoken>

Which returns something like this:

{
  "console": {
    "instance_uuid": <uuid>,
    "host": <hypervisor>,
    "port": <a TCP port number>,
    "tls_port": <another TCP port number>,
    "internal_access_path": null
  }
}

APIImpact

Change-Id: I1e701cbabc0e2c435685e31465159eec09e3b1a0

api-ref/source/parameters.yaml

@@ -5993,8 +5993,9 @@ remote_console_protocol:
 remote_console_type:
   description: |
     The type of remote console. The valid values are ``novnc``,
-    ``spice-html5``, ``serial``, and ``webmks``. The type
-    ``webmks`` is added since Microversion ``2.8``.
+    ``spice-html5``, ``spice-direct``, ``serial``, and ``webmks``. The type
+    ``webmks`` was added in Microversion ``2.8``, and the type
+    ``spice-direct`` was added in Microversion ``2.99``.
   in: body
   required: true
   type: string
@@ -7102,6 +7103,12 @@ tenant_usages:
   in: body
   required: true
   type: array
+tls_port_number:
+  description: |
+    The port number of a port requiring a TLS connection.
+  in: body
+  required: false
+  type: integer
 to_port:
   description: |
     The port at end of range.