feat(compute): support user data update during rebuild

Author: Adrien Pensart

openstack/compute/v2/servers/requests.go

@@ -486,6 +486,10 @@ type RebuildOpts struct {
 	// Personality [optional] includes files to inject into the server at launch.
 	// Rebuild will base64-encode file contents for you.
 	Personality Personality `json:"personality,omitempty"`
+
+    // Configuration information or scripts to use upon rebuild. Must be Base64 encoded. Restricted to 65535 bytes.
+    // If null is specified, the existing user_data is unset.
+    UserData *string `json:"user_data"`
 }
 
 // ToServerRebuildMap formats a RebuildOpts struct into a map for use in JSON