Add ServerOptions to initial server startup logs (#794)

### What

Add ServerOptions to initial server startup logs.

![image](https://github.com/hasura/v3-engine/assets/358550/33e49344-a7d8-44be-8bce-b6c8b11a06ec)

### Update

Use json, as well as a span field rather than an event:

![image](https://github.com/hasura/v3-engine/assets/358550/724bcdf4-8125-4a5e-83aa-db7de1229e3a)

V3_GIT_ORIGIN_REV_ID: 28d0c8edd70357b3460a4fbea389f5fa801fd4bf

v3/crates/engine/bin/engine/main.rs

@@ -18,11 +18,12 @@ use pre_execution_plugin::{
     configuration::PrePluginConfig, execute::pre_execution_plugins_handler,
 };
 use reqwest::header::CONTENT_TYPE;
+use serde::Serialize;
 use tower_http::cors::CorsLayer;
 use tower_http::trace::TraceLayer;
 use tracing_util::{
-    add_event_on_active_span, set_status_on_current_span, ErrorVisibility, SpanVisibility,
-    TraceableError, TraceableHttpResponse,
+    add_event_on_active_span, set_attribute_on_active_span, set_status_on_current_span,
+    ErrorVisibility, SpanVisibility, TraceableError, TraceableHttpResponse,
 };
 
 use base64::engine::Engine;
@@ -52,7 +53,7 @@ const DEFAULT_PORT: u16 = 3000;
 const MB: usize = 1_048_576;
 
 #[allow(clippy::struct_excessive_bools)] // booleans are pretty useful here
-#[derive(Parser)]
+#[derive(Parser, Serialize)]
 #[command(version = VERSION)]
 struct ServerOptions {
     /// The path to the metadata file, used to construct the schema.g
@@ -385,6 +386,12 @@ async fn start_engine(server: &ServerOptions) -> Result<(), StartupError> {
     println!("{log}");
     add_event_on_active_span(log);
 
+    set_attribute_on_active_span(
+        tracing_util::AttributeVisibility::Internal,
+        "server_options",
+        serde_json::to_string_pretty(server).unwrap_or_else(|err| err.to_string()),
+    );
+
     // run it with hyper on `addr`
     axum::Server::bind(&address)
         .serve(engine_router.into_make_service())

v3/crates/engine/src/internal_flags.rs

@@ -4,7 +4,16 @@
 /// If we want to start offering user control of these, they should move out of here and into the
 /// flags in Metadata, nothing here should be depended on.
 #[derive(
-    Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, clap::ValueEnum, serde::Deserialize,
+    Debug,
+    Clone,
+    Copy,
+    PartialEq,
+    Eq,
+    PartialOrd,
+    Ord,
+    clap::ValueEnum,
+    serde::Deserialize,
+    serde::Serialize,
 )]
 #[serde(rename_all = "snake_case")]
 pub enum UnstableFeature {