Create Rust-based openai api proxy server in node hub (#678)

This is a Rust-based version of #676
based on
https://github.com/LlamaEdge/LlamaEdge/tree/main/llama-api-server . It
includes `serde` structs to fully deserialize chat completion requests.

The server replies to requests asynchronously, which makes it possible
to serve multiple clients at the same time. Note that replies are mapped
to requests purely based on their order right now. So the first reply is
assigned to the first request and so on. If the order of replies is
different (e.g. because some completions take longer), some form of ID
needs to be added to the code to enable a proper `request<->reply`
mapping.

Like #676, this PR only implements basic chat completion requests. You
can try it through these steps:

```bash
cd examples/openai-server
dora build dataflow-rust.yml
dora start dataflow-rust.yml

# In a separate terminal
python openai_api_client.py
```

I didn't implement the `/v1/models` endpoint, so the _"Testing API
endpoints..."_ part of `openai_api_client.py` is expected to fail with
_"Error listing models: 404"_.

Cargo.toml

@@ -33,6 +33,7 @@ members = [
     "node-hub/dora-record",
     "node-hub/dora-rerun",
     "node-hub/terminal-print",
+    "node-hub/openai-proxy-server",
     "libraries/extensions/ros2-bridge",
     "libraries/extensions/ros2-bridge/msg-gen",
     "libraries/extensions/ros2-bridge/python",

examples/openai-server/dataflow-rust.yml

@@ -0,0 +1,16 @@
+nodes:
+  - id: dora-openai-server
+    build: cargo build -p dora-openai-proxy-server --release
+    path: ../../target/release/dora-openai-proxy-server
+    outputs:
+      - chat_completion_request
+    inputs:
+      completion_reply: dora-echo/echo
+
+  - id: dora-echo
+    build: pip install -e ../../node-hub/dora-echo
+    path: dora-echo
+    inputs:
+      echo: dora-openai-server/chat_completion_request
+    outputs:
+      - echo

node-hub/openai-proxy-server/Cargo.toml

@@ -0,0 +1,27 @@
+[package]
+name = "dora-openai-proxy-server"
+version.workspace = true
+edition = "2021"
+documentation.workspace = true
+description.workspace = true
+license.workspace = true
+repository.workspace = true
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+tokio = { version = "1.36.0", features = ["full"] }
+dora-node-api = { workspace = true, features = ["tracing"] }
+eyre = "0.6.8"
+chrono = "0.4.31"
+tracing = "0.1.27"
+serde = { version = "1.0.130", features = ["derive"] }
+serde_json = "1.0.68"
+url = "2.2.2"
+indexmap = { version = "2.6.0", features = ["serde"] }
+hyper = { version = "0.14", features = ["full"] }
+thiserror = "1.0.37"
+uuid = { version = "1.10", features = ["v4"] }
+mime_guess = "2.0.4"
+futures = "0.3.31"
+tokio-stream = "0.1.11"