feat(otel): Add spec for SentryPropagator

src/docs/sdk/performance/opentelemetry.mdx

@@ -152,17 +152,51 @@ const sdk = new NodeSDK({
 });
 ```
 
-### Step 2: Define `isSentryRequest`
+### Step 2: Implement the SentryPropagator on your SDK Add SentryPropagator
 
-We want to make sure we don't create spans that represent requests to Sentry
+`SentryPropagator` is used to inject/extract `sentry-trace` and `baggage` headers to make trace propogation and dynamic sampling work correctly.
 
-TODO @neel
+```ts
+import { Context, TextMapPropagator } from "@opentelemetry/api";
+import { SpanContext } from "@opentelemetry/api";
+
+export class SentryPropagator implements TextMapPropagator {
+  inject(context: Context, carrier: unknown, setter: TextMapSetter): void {
+    const spanContext = getSpanContext(context);
+    if (isSentryRequest(spanContext)) {
+      return;
+    }
+
+    const sentryTrace = generateSentryTrace(spanContext);
+    setSentryTraceHeader(carrier, sentryTrace, setter);
+
+    const baggage = generateBaggageFromContext(context);
+    setBaggageHeader(carrier, baggage, setter);
+  }
+
+  extract(context: Context, carrier: unknown, getter: TextMapGetter): Context {
+    const sentryTraceParent = extractSentryTraceFromCarrier(carrier, getter);
+    setSentryTraceInfoOnSpanContext(context, sentryTraceParent);
+
+    const dynamicSamplingContext = extractBaggageFromCarrier(carrier, getter);
+    setDynamicSamplingContextOnSpanContext(context, dynamicSamplingContext);
+
+    return context;
+  }
+}
+```
+
+### Step 3: Define `isSentryRequest`
+
+We want to make sure that we don't create Sentry Spans for requests to Sentry.
+
+TODO: We need to make sure we filter these out somehow. Spec WIP
 
 ### Step 3: Define `getTraceData`
 
 We want to make sure a transaction is started with information from the `sentry-trace` and `baggage` headers.
 
-TODO @neel
+If the user is using the `SentryPropagator`, the `sentry-trace` information should be getting attached to incoming spans automatically. This should mean that we don't need to explicitly grab the header. The `SentryPropagator` should also be putting the Dynamic Sampling Context from the baggage header onto the OpenTelemetry Context, which then can be used in `getTraceData` to inject the DSC in during transaction creation.
 
 ### Step 4: Define `updateSpanWithOtelData`