Digest HTTP Auth for wallet JSON RPC should be reused

Once a wallet object is instantiated, all calls to it invoke a new HTTPDigestAuth object.

I think this should be cached, or some kind of requests session used.

Let's say you have pseudocode like this:

wallet = JSONRPCWallet(user="user", pass="pass")
wallet.height()  # This attempts with no auth, gets 401ed and a nonce returned, then attempts again with auth.
wallet.height()  # This doesn't cache the old nonce, because the HTTPDigestAuth object is lost, so it does it all over again.

I think we can make the HTTPDigestAuth object once here: https://github.com/monero-ecosystem/monero-python/blob/master/monero/backends/jsonrpc/daemon.py#L26

This way there's only one time getting the digest, and follow up commands are much faster.

Maybe:

self._auth = requests.auth.HTTPDigestAuth(user, password) in __init__()?

We might not even have to set self.user and self.password with this.

Let me know if this doesn't make sense or anything like that.

Thank you!

[emesik]

This sounds good, however I don't have a test environment right now. All the nodes I host or know are open.

Ok, let me see if I can test this. Thanks!

Had to add a requests.Session() as well, but unit tests are passing for me and it's running perfectly against my Monero node. This won't be so substantial of a performance improvement for local use, but can definitely notice it with remote nodes.

@emesik could you take a look at this when you have the chance?

[emesik]

Sure, but I have quite busy time right now. Will probably sit down and push development around Christmas.

Thank you! You've been busy!