docs(telemetry.apollo): add documentation about send_headers and `s…

…end_variable_value` (#2435)

NEXT_CHANGELOG.md

@@ -123,6 +123,23 @@ By [@Geal](https://github.com/geal) in https://github.com/apollographql/router/p
 
 ## 📚 Documentation
 
+### `send_headers` and `send_variable_values` in `telemetry.apollo` ([Issue #2149](https://github.com/apollographql/router/issues/2149))
+
++ `send_headers`
+
+  Provide this field to configure which request header names and values are included in trace data that's sent to Apollo Studio. Valid options are: `only` with an array, `except` with an array, `none`, `all`.
+
+  The default value is `none``, which means no header names or values are sent to Studio. This is a security measure to prevent sensitive data from potentially reaching the Router.
+
++ `send_variable_values`
+
+  Provide this field to configure which variable values are included in trace data that's sent to Apollo Studio. Valid options are: `only` with an array, `except` with an array, `none`, `all`.
+
+  The default value is `none`, which means no variable values are sent to Studio. This is a security measure to prevent sensitive data from potentially reaching the Router.
+
+
+By [@bnjjj](https://github.com/bnjjj) in https://github.com/apollographql/router/pull/2435
+
 ### Documentation on how to propagate headers between subgraph services ([Issue #2128](https://github.com/apollographql/router/issues/2128))
 
 Migrating headers between subgraph services is possible via Rhai script. An example has been added to the header propagation page.

docs/source/configuration/apollo-telemetry.mdx

@@ -42,6 +42,18 @@ Note that `field_level_instrumentation_sampler` may not sample at a greater rate
 
 ## Advanced configuration
 
+### `send_headers`
+
+Provide this field to configure which request header names and values are included in trace data that's sent to Apollo Studio. Valid options are: `only` with an array, `except` with an array, `none`, `all`.
+
+The default value is `none`, which means no header names or values are sent to Studio. This is a security measure to prevent sensitive data from leaving your infrastructure unless you specifically opt into it
+
+### `send_variable_values`
+
+Provide this field to configure which variable values are included in trace data that's sent to Apollo Studio. Valid options are: `only` with an array, `except` with an array, `none`, `all`.
+
+The default value is `none`, which means no variable values are sent to Studio. This is a security measure to prevent sensitive data from leaving your infrastructure unless you specifically opt into it.
+
 ```yaml title="router.yaml"
 telemetry:
   apollo: