add user translation logic (#406)

Author: willarmiros

src/docs/getting-started/x-ray.mdx

@@ -98,6 +98,7 @@ exporters:
 | Status.StatusCode                                                             | throttle               | <ul><li> When StatusCode = Error then error is set to true for a 429 HTTP response. The exception stack trace is captured in the exception field. Any other values of StatusCode result in throttle being set to false.    </li></ul>                                                                                                                                                                                                                                                                                                                                                                                  |
 | Event                                                                         | exception              | <ul><li> This field is populated by span exception events when the StatusCode = Error ; all other span events are dropped.   </li></ul>                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
 | Link                                                                          | N/A                    | <ul><li> Not currently supported by the exporter.    </li></ul>                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
+| enduser.id                                             | user                 | <ul><li> This field is only populated on X-Ray segments, not subsegments. </li></ul>                                                                                                                                                                                                                                                 |
 | cloud.provider and cloud.platform                                             | origin                 | <ul><li> If value of `cloud.provider` attribute key within span resource attributes = “aws", then the exporter copies the value from cloud.platform attribute key to the origin field, if the cloud.platform key is one of the following supported values: `aws_app_runner`, `aws_eks`, `aws_elastic_beanstalk`, `aws_ecs` and `aws_ec2`. Any other cloud.platform key values then origin will not be set.  </li></ul>                                                                                                                                                                                                                                                 |
 | rpc.system and aws.service                                                    | namespace              | <ul><li> If namespace has not yet been set, and one of the following conditions is true, then namespace will be set to "aws": - rpc.system attribute key = "aws-api" - aws.service attribute key is not empty.  </li><li> If namespace has not yet been set, and spankind = "client", then namespace is set to "remote".  In all other cases, namespace is not set.   </li></ul>                                                                                                                                                                                                                                       |
 | peer.service, aws.service, db.service, service.name, span.kind, and span name | name                   | <ul><li> Name field is set to peer.service if not empty.  </li><li> If peer.service is empty and aws.service attribute key is not empty, name is set to aws.service.  </li><li> If aws.service is empty and db.service attribute key is not empty, name is set to db.service.  </li><li> If none of these attribute keys has a value, and span.kind = "Server", then name is set to value of service.name attribute key.  </li><li> If none of the prior conditions are met, name is set to the name of the span.       </li></ul>                                                                                     |