Document the X-Opaque-Id header (#8820)

* Document the `X-Opaque-Id` header

A [bug][1] was recently identified related to this header that was partly
exascerbated by a misuse of the field. We have some documentation related to the
[Tasks][2] API for this field, but no general guidance on how to use it.

[1]: opensearch-project/OpenSearch#16702
[2]: https://opensearch.org/docs/latest/api-reference/tasks/#attaching-headers-to-tasks

Signed-off-by: Andrew Ross <andrross@amazon.com>

* Update _api-reference/common-parameters.md

Co-authored-by: kolchfa-aws <105444904+kolchfa-aws@users.noreply.github.com>
Signed-off-by: Andrew Ross <andrross@amazon.com>

* Update _api-reference/common-parameters.md

Co-authored-by: kolchfa-aws <105444904+kolchfa-aws@users.noreply.github.com>
Signed-off-by: Andrew Ross <andrross@amazon.com>

* Update _api-reference/common-parameters.md

Co-authored-by: kolchfa-aws <105444904+kolchfa-aws@users.noreply.github.com>
Signed-off-by: Andrew Ross <andrross@amazon.com>

* Update _api-reference/common-parameters.md

Co-authored-by: Nathan Bower <nbower@amazon.com>
Signed-off-by: Andrew Ross <andrross@amazon.com>

* Update _api-reference/common-parameters.md

Co-authored-by: Nathan Bower <nbower@amazon.com>
Signed-off-by: Andrew Ross <andrross@amazon.com>

---------

Signed-off-by: Andrew Ross <andrross@amazon.com>
Co-authored-by: kolchfa-aws <105444904+kolchfa-aws@users.noreply.github.com>
Co-authored-by: Nathan Bower <nbower@amazon.com>

_api-reference/common-parameters.md

@@ -123,4 +123,17 @@ Kilometers | `km` or `kilometers`
 Meters | `m` or `meters`
 Centimeters | `cm` or `centimeters`
 Millimeters | `mm` or `millimeters`
-Nautical miles | `NM`, `nmi`, or `nauticalmiles` 
+Nautical miles | `NM`, `nmi`, or `nauticalmiles` 
+
+## `X-Opaque-Id` header
+
+You can specify an opaque identifier for any request using the `X-Opaque-Id` header. This identifier is used to track tasks and deduplicate deprecation warnings in server-side logs. This identifier is used to differentiate between callers sending requests to your OpenSearch cluster. Do not specify a unique value per request.
+
+#### Example request
+
+The following request adds an opaque ID to the request:
+
+```json
+curl -H "X-Opaque-Id: my-curl-client-1" -XGET localhost:9200/_tasks
+```
+{% include copy.html %}