Rename headers to header.

docs/features/http_mdc_header.md

@@ -0,0 +1,28 @@
+# Add HTTP headers to MDC
+
+## Properties
+
+Property | Description | Default
+-------- | ----------- | -------
+`logger.http.header.enabled` | filter enabled? | `true`
+`logger.http.header.path` | filter path | `/**`
+`logger.http.header.order` | order for [Ordered](https://github.com/micronaut-projects/micronaut-core/blob/v3.2.0/core/src/main/java/io/micronaut/core/order/Ordered.java) | [ServerFilterPhase.FIRST.before()](https://github.com/micronaut-projects/micronaut-core/blob/v3.2.0/http/src/main/java/io/micronaut/http/filter/ServerFilterPhase.java#L34)
+`logger.http.header.prefix` | prefix to MDC key | ``
+`logger.http.header.names` | http header names to add to MDC | `[]`
+
+## Examples
+
+Configuration for b3-propagation:
+
+```yaml
+logger:
+  http:
+    header:
+      prefix: header.
+      names:
+        - x-request-id
+        - x-b3-traceId 
+        - x-b3-parentspanid
+        - x-b3-spanid
+        - x-b3-sampled 
+```