Add remote rpc support

[eddiewang]

Never written rust before, so might need some polish here before it's merge ready.
Mainly quality of life improvements for users that aren't using a localhost Bitcoin node.

• Adds rpc_user and rpc_pass arguments to the binary
• Uses rpc_user / rpc_pass if arguments exist, otherwise defaults back to cookie mode
• Ensures all wallet commands properly pass the /wallet/ even if the rpc_url is set

[ghost]

Concept ACK

What happens if only username or password is provided and one argument is missing?

[eddiewang]

Right now, the logic will default to cookie unless both arguments are provided.
My understanding of how .is_none() works is that if the value is set, even if it's to an empty string "", it should still return False.

If my assumption is correct, I think the desired state is to explicitly pass in both the user and pass in order to activate this mode, defaulting to the cookie approach otherwise.

[AngusP]

rpc_pass and rpc_user are Option<String>, which you can get at in a nicer way than checking ! is_none() then calling unwrap() (calling unwrap is generally (strongly) discouraged), by using if let and destructuring:

let number = Some(7);
let another = Some(12);
let missing: Option<i32> = None;

if let (Some(i), Some(j)) = (number, another) {
    println!("Matched {:?} and {:?}!", i, j);
}
// ^ Prints "Matched 7 and 12!"

if let (Some(i), Some(j)) = (number, missing) {
    println!("Matched {:?} and {:?}!", i, j);
} else {
    println!("Didn't match");
}
// ^ Prints "Didn't match"

so something like

Suggested change

	let auth = if !rpc_pass.is_none() && !rpc_user.is_none() {
	let ruser = rpc_user.unwrap();
	let rpass = rpc_pass.unwrap();
	log::info!("Using RPC credentials from command line {ruser}");
	if let (Some(rpass), Some(ruser)) = (rpc_pass, rpc_user) {
	log::info!("Using RPC credentials from command line {ruser}");

(Caveat I'm also a Rust noob so if the compiler complains, sorry!)

[AngusP]

Also note #1527 was trying to add this as well

[raphjaph]

We added this check out PR #1527