swarm-queue-client: add an authenticated HttpClient for OTLP exporters (otel-auth feature)

Cargo.toml

@@ -144,6 +144,29 @@ opentelemetry-otlp = { version = "0.32", default-features = false, features = [
   "reqwest-blocking-client",
   "reqwest-rustls",
 ] }
+# The trait an OTLP exporter's HTTP transport is built on
+# (`opentelemetry_otlp::WithHttpConfig::with_http_client`) — pulled in
+# directly (not just transitively via `opentelemetry-otlp` above) by
+# `swarm-queue-client`'s `otel-auth` feature, which implements the trait
+# itself rather than using the crate's own blanket `reqwest`/
+# `reqwest-blocking` impls (this workspace's implementation needs to mint
+# a fresh bearer token per request, which no blanket impl can do). No
+# extra cargo features requested here for exactly that reason — the
+# blanket impls live behind `reqwest`/`reqwest-blocking` features this
+# workspace never turns on for this crate.
+opentelemetry-http = "0.32"
+# `async-trait`: `opentelemetry_http::HttpClient` predates stable
+# `async fn` in traits and is still expressed with this macro upstream —
+# implementing the trait (rather than only consuming the crate's own
+# blanket impls) means writing `#[async_trait::async_trait]` on the impl
+# block to match its expansion.
+async-trait = "0.1"
+# `bytes`/`http`: the payload and request/response types
+# `opentelemetry_http::HttpClient::send_bytes` is expressed in terms of —
+# needed to implement the trait, not just call something that already
+# does.
+bytes = "1"
+http = "1"
 http-body-util = "0.1"
 # ⚠️ Keep at 0.11.1 or newer, and keep it on the SAME reqwest as everything
 # else. 0.11.0 links reqwest 0.12 while the workspace is on 0.13, and cargo