[WIP] Post inventory to server after install

[eriknordmark]

This introduces a eve_inventory_server URL which can either be set from ipxe or in config/grub.cfg. If that is set it the EVE-OS will POST to that URL when it boots after the install is complete. The POSTs are retried until they are all accepted by the server at that URL.

This initial implementation does not use any secure client identifier hence only makes sense with server on a locally secure network. A possible improvement is to use the /config/onboarding.key.pem to sign the payloads using the authcontainer we use for the rest of the API, but that implies a server which does authcontainer verification and protobuf decode of the payloads.

[rvs]

Hey @eriknordmark -- I see changes, but you still planning to move this all the way to /persist correct?

[eriknordmark]

Hey @eriknordmark -- I see changes, but you still planning to move this all the way to /persist correct?

Either that (which means running the storage-init container at install time to create /persist), or use the network to push the inventory to the server (including retrying forever?) to the inventory server. In the latter case we don't need to save it on the device.

But there are some benefits of having the model json (in particular the iommu groups) as determined at install time before we boot into some particular hypervisor and save that for when EVE-OS is running. So that means creating /persist/