Run-time, mutable metadata for VMs

OpenStack currently supports a metadata server (nova-metadata) that is implemented as a separate server - requests to it are port-forwarded through the nova API. An API request will return metadata for the instance associated with the source IP of the API call. This way only the VM can access this data (for obvious security reasons). Currently this data is read-only and cannot be modified after the VM instance is launched. Also there is a key “user_data” that holds a value that is passed in when the VM is provisioned.

Add the ability to edit VM instance metadata at run-time. Enable this data to be read or edited by any authenticated client.