feat: make auth interface more generic

[miraclx]

This makes the auth interface more generic, primarily to extend the flexibility of custom implementations. Allowing them to be able to customize their header names.

use near_jsonrpc_client::auth;

struct CustomUserAuth {
    username: String,
    password: zeroize::Zeroizing<String>
}

impl auth::AuthScheme for CustomUserAuth {
    fn get_auth_header(&self) -> auth::AuthHeaderEntry {
        auth::AuthHeaderEntry {
            header: "Authorization".to_string(),
            token: format!("Basic {}", base64::encode(format!("{}:{}", self.username, *self.password))),
        }
    }
}

let client = JsonRpcClient::connect("http://localhost:3030")
    .auth(CustomUserAuth { username: "root", password: "n1c3_try".to_string().into() });

Also replaces Authorization: Basic <token> with x-api-key: <token>.

let client = JsonRpcClient::connect("http://localhost:3030")
    .auth(BasicAuth { token: "our-secret-token" });

Now becomes;

1.  let client = JsonRpcClient::connect("http://localhost:3030")
        .auth(ApiKey::Plain("our-secret-token"));

   - or -

2.  let client = JsonRpcClient::connect("http://localhost:3030")
        .auth(ApiKey::Base64("b3VyLXNlY3JldC10b2tlbg=="));

[chefsale]

Good stuff