fix: Add signal-specific path components to OtelConfig's default endpoints

Fixes wasmCloud#2265

Signed-off-by: Joonas Bergius <joonas@cosmonic.com>

Author: joonas

crates/core/src/otel.rs

@@ -40,23 +40,23 @@ impl OtelConfig {
         self.logs_endpoint.clone().unwrap_or_else(|| {
             self.observability_endpoint
                 .clone()
-                .unwrap_or_else(|| self.default_endpoint().to_string())
+                .unwrap_or_else(|| self.default_endpoint(OtelSignal::Logs))
         })
     }
 
     pub fn metrics_endpoint(&self) -> String {
         self.metrics_endpoint.clone().unwrap_or_else(|| {
             self.observability_endpoint
                 .clone()
-                .unwrap_or_else(|| self.default_endpoint().to_string())
+                .unwrap_or_else(|| self.default_endpoint(OtelSignal::Metrics))
         })
     }
 
     pub fn traces_endpoint(&self) -> String {
         self.traces_endpoint.clone().unwrap_or_else(|| {
             self.observability_endpoint
                 .clone()
-                .unwrap_or_else(|| self.default_endpoint().to_string())
+                .unwrap_or_else(|| self.default_endpoint(OtelSignal::Traces))
         })
     }
 
@@ -72,10 +72,20 @@ impl OtelConfig {
         self.enable_traces.unwrap_or(self.enable_observability)
     }
 
-    fn default_endpoint(&self) -> &str {
+    fn default_endpoint(&self, signal: OtelSignal) -> String {
         match self.protocol {
-            OtelProtocol::Grpc => OTEL_EXPORTER_OTLP_GRPC_ENDPOINT_DEFAULT,
-            OtelProtocol::Http => OTEL_EXPORTER_OTLP_HTTP_ENDPOINT_DEFAULT,
+            // gRPC endpoint does not include any signal specific path components.
+            OtelProtocol::Grpc => OTEL_EXPORTER_OTLP_GRPC_ENDPOINT_DEFAULT.to_string(),
+            // http endpoint includes a signal-specific path component.
+            OtelProtocol::Http => match signal {
+                OtelSignal::Traces => {
+                    format!("{}/v1/traces", OTEL_EXPORTER_OTLP_HTTP_ENDPOINT_DEFAULT)
+                }
+                OtelSignal::Metrics => {
+                    format!("{}/v1/metrics", OTEL_EXPORTER_OTLP_HTTP_ENDPOINT_DEFAULT)
+                }
+                OtelSignal::Logs => format!("{}/v1/logs", OTEL_EXPORTER_OTLP_HTTP_ENDPOINT_DEFAULT),
+            },
         }
     }
 }
@@ -86,6 +96,13 @@ pub enum OtelProtocol {
     Http,
 }
 
+// Represents https://opentelemetry.io/docs/concepts/signals/
+enum OtelSignal {
+    Traces,
+    Metrics,
+    Logs,
+}
+
 impl Default for OtelProtocol {
     fn default() -> Self {
         Self::Http