[vsnation]

Fix: beam-wallet export_owner_key --owner_key_pass=<pw> encrypts the exported owner (viewer) key with its own password, so the node that uses it doesn't need the wallet password (#401; option A of #891).

Why: the key was always encrypted with the wallet password, and beam-node --owner_key=… --pass=… needs that password to use it. Anyone running a node that watches their wallet (often a remote server, started by systemd) had to put the wallet password into the node's command line or config.

How to see the bug (master)

beam-wallet restore --pass=walletpw --wallet_path=w.db --seed_phrase="abandon;abandon;abandon;abandon;abandon;abandon;abandon;abandon;abandon;abandon;abandon;about;"
beam-wallet export_owner_key --pass=walletpw --wallet_path=w.db
beam-node --owner_key=<key> --pass=walletpw     # the wallet password has to go to the node
beam-wallet export_owner_key --pass=walletpw --wallet_path=w.db --owner_key_pass=nodepw
# master: "unrecognised option '--owner_key_pass'"

Improvement

	master	this PR
export_owner_key (no option)	key encrypted with the wallet password	the same key as master, plus a hint: "The key is encrypted with the wallet password. Use --owner_key_pass to encrypt it with a different password for the node"
export_owner_key --owner_key_pass=nodepw	unrecognised option	key encrypted with nodepw; "Give the node that password, not the wallet password."
beam-node --owner_key=<that key> --pass=nodepw	–	node starts and uses the key
beam-node --owner_key=<that key> --pass=walletpw	–	key import failed
--owner_key_pass ""	–	--owner_key_pass must not be empty

Nodes need no changes: they already take the key's password through --pass.

Testing: all rows above were run with master's and this branch's beam-wallet, and with this branch's beam-node. Fork CI (running): https://github.com/vsnation/beam/actions/runs/

Fixes #401