Remove experimental_when_header feature

docs/source/reference/migration/from-router-v1.mdx

@@ -58,6 +58,69 @@ telemetry:
     metrics_reference_mode: standard
 ```
 
+### Logging
+
+If you used the `experimental_when_header` feature previously like this for example:
+
+```yaml title="router.previous.yaml"
+telemetry:
+  exporters:
+    logging:
+      # If one of these headers matches we will log supergraph and subgraphs requests/responses
+      experimental_when_header: # REMOVED
+        - name: apollo-router-log-request
+          value: my_client
+          headers: true # default: false
+          body: true # default: false
+```
+
+This feature not longer exists and can be replaced with another one included in custom telemetry. Here is an example on how you could have the same behavior with the new configuration:
+
+```yaml title="router.yaml"
+telemetry:
+  instrumentation:
+    events:
+      router:
+        request: # Display router request log
+          level: info
+          condition:
+            eq:
+            - request_header: apollo-router-log-request
+            - my_client
+        response: # Display router response log
+          level: info
+          condition:
+            eq:
+            - request_header: apollo-router-log-request
+            - my_client
+      supergraph:
+        request: # Display supergraph request log
+          level: info
+          condition:
+            eq:
+            - request_header: apollo-router-log-request
+            - my_client
+        response:
+          level: info
+          condition:
+            eq:
+            - request_header: apollo-router-log-request
+            - my_client
+      subgraph:
+        request: # Display subgraph request log
+          level: info
+          condition:
+            eq:
+            - supergraph_request_header: apollo-router-log-request
+            - my_client
+        response: # Display subgraph response log
+          level: info
+          condition:
+            eq:
+            - supergraph_request_header: apollo-router-log-request
+            - my_client
+```
+
 ### Deploy your router
 
 Make sure that you are referencing the correct router release: **v2.0.0-preview.0**

docs/source/reference/router/telemetry/instrumentation/selectors.mdx

@@ -89,6 +89,7 @@ The subgraph service executes multiple times during query execution, with each e
 | `supergraph_operation_kind` | Yes         | `string`         | The operation kind from the supergraph query                                   |
 | `supergraph_query`          | Yes         | `string`         | The graphql query to the supergraph                                            |
 | `supergraph_query_variable` | Yes         |                  | The name of a supergraph query variable                                        |
+| `supergraph_request_header` | Yes         |                  | The name of a supergraph request header                                        |
 | `request_context`           | Yes         |                  | The name of a request context key                                              |
 | `response_context`          | Yes         |                  | The name of a response context key                                             |
 | `baggage`                   | Yes         |                  | The name of a baggage item                                                     |