Soroban-RPC: allow quering the current env interface

[willemneal]

What problem does your feature solve?

CLI requests to futurenet are failing for contracts that are compiled with an SDK that uses a env interface greater than futurenet.

Eventually env interface version will be versioned by protocol version so this shouldn't be an issue then, but until then it would be nice to allow the CLI to provide a better error message if the env version of the contract being deployed is not ahead of the RPC.

cc @paulbellamy @leighmcculloch

What would you like to see?

An RPC method to get the current env interface version

What alternatives are there?

[leighmcculloch]

@graydon Is env interface version going away soon? I got the impression it was a very near future thing.

[leighmcculloch]

Looks like this was done at some point. The interface version is the protocol version. (The pre-release component of the interface version is no longer used, so it is simply the protocol version.) The protocol version is retrievable from the rpc now via the getNetwork method.

$ curl -fsSL https://mainnet.sorobanrpc.com -H 'Content-Type: application/json' -d '{"jsonrpc":"2.0","id":"0","method":"getNetwork"}'
{"jsonrpc":"2.0","id":"0","result":{"passphrase":"Public Global Stellar Network ; September 2015","protocolVersion":24}}