Improve tracing

docs/content/observability/tracing/datadog.md

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+# DataDog
+
+To enable the DataDog:
+
+```toml tab="File"
+[tracing]
+  [tracing.datadog]
+```
+
+```bash tab="CLI"
+--tracing
+--tracing.datadog
+```
+
+#### `localAgentHostPort`
+
+_Required, Default="127.0.0.1:8126"_
+
+Local Agent Host Port instructs reporter to send spans to datadog-tracing-agent at this address.
+
+```toml tab="File"
+[tracing]
+  [tracing.datadog]
+    localAgentHostPort = "127.0.0.1:8126"
+```
+
+```bash tab="CLI"
+--tracing
+--tracing.datadog.localAgentHostPort="127.0.0.1:8126"
+```
+
+#### `debug`
+
+_Optional, Default=false_
+
+Enable DataDog debug.
+
+```toml tab="File"
+[tracing]
+  [tracing.datadog]
+    debug = true
+```
+
+```bash tab="CLI"
+--tracing
+--tracing.datadog.debug=true
+```
+
+#### `globalTag`
+
+_Optional, Default=empty_
+
+Apply shared tag in a form of Key:Value to all the traces.
+
+```toml tab="File"
+[tracing]
+  [tracing.datadog]
+    globalTag = "sample"
+```
+
+```bash tab="CLI"
+--tracing
+--tracing.datadog.globalTag="sample"
+```
+
+#### `prioritySampling`
+
+_Optional, Default=false_
+
+Enable priority sampling. When using distributed tracing,
+this option must be enabled in order to get all the parts of a distributed trace sampled.
+
+```toml tab="File"
+[tracing]
+  [tracing.datadog]
+    prioritySampling = true
+```
+
+```bash tab="CLI"
+--tracing
+--tracing.datadog.prioritySampling=true
+```