fix: Manually encode Authorization header for eventsource_client (#2284)

## Linked Issues/PRs
This PR is a band-aid fix;
#2283 suggests alternatives
to `eventsource_client`.

## Description
<!-- List of detailed changes -->

`eventsource_client` (and `hyper` under the hood) do not pass
`username:password` from the URL into the `Authorization` header. This
PR adds the header manually, encoding the credentials as base64 per the
[Basic HTTP Authentication
RFC](https://datatracker.ietf.org/doc/html/rfc7617#section-2).

## Checklist
- [x] Breaking changes are clearly marked as such in the PR description
and changelog
- [ ] New behavior is reflected in tests
- [x] [The specification](https://github.com/FuelLabs/fuel-specs/)
matches the implemented behavior (link update PR if changes are needed)

### Before requesting review
- [x] I have reviewed the code myself
- [x] I have created follow-up issues caused by this PR and linked them
here

### After merging, notify other teams

[Add or remove entries as needed]

- [ ] [Rust SDK](https://github.com/FuelLabs/fuels-rs/)

---------

Co-authored-by: Green Baneling <XgreenX9999@gmail.com>

crates/client/Cargo.toml

@@ -12,9 +12,10 @@ description = "Tx client and schema specification."
 
 [dependencies]
 anyhow = { workspace = true }
+base64 = { version = "0.22.1", optional = true }
 cynic = { workspace = true }
 derive_more = { workspace = true }
-eventsource-client = { version = "0.12.2", optional = true }
+eventsource-client = { version = "0.13.0", optional = true }
 fuel-core-types = { workspace = true, features = ["alloc", "serde"] }
 futures = { workspace = true, optional = true }
 hex = { workspace = true }
@@ -46,4 +47,4 @@ serde_json = { version = "1.0", features = ["raw_value"] }
 std = ["fuel-core-types/std"]
 default = ["subscriptions", "std"]
 test-helpers = []
-subscriptions = ["eventsource-client", "futures", "hyper-rustls"]
+subscriptions = ["base64", "eventsource-client", "futures", "hyper-rustls"]

crates/client/src/client.rs

@@ -29,6 +29,11 @@ use crate::client::{
 };
 use anyhow::Context;
 #[cfg(feature = "subscriptions")]
+use base64::prelude::{
+    Engine as _,
+    BASE64_STANDARD,
+};
+#[cfg(feature = "subscriptions")]
 use cynic::StreamingOperation;
 use cynic::{
     http::ReqwestExt,
@@ -270,6 +275,19 @@ impl FuelClient {
                     format!("Failed to add header to client {e:?}"),
                 )
             })?;
+        if let Some(password) = url.password() {
+            let username = url.username();
+            let credentials = format!("{}:{}", username, password);
+            let authorization = format!("Basic {}", BASE64_STANDARD.encode(credentials));
+            client_builder = client_builder
+                .header("Authorization", &authorization)
+                .map_err(|e| {
+                    io::Error::new(
+                        io::ErrorKind::Other,
+                        format!("Failed to add header to client {e:?}"),
+                    )
+                })?;
+        }
 
         if let Some(value) = self.cookie.deref().cookies(&self.url) {
             let value = value.to_str().map_err(|e| {