feat: add user_name field to the finding access

packages/google-cloud-securitycenter/protos/google/cloud/securitycenter/v1/access.proto

@@ -42,7 +42,7 @@ message Access {
   // The caller IP's geolocation, which identifies where the call came from.
   Geolocation caller_ip_geo = 3;
 
-  // What kind of user agent is associated, e.g. operating system shells,
+  // What kind of user agent is associated, for example operating system shells,
   // embedded or stand-alone applications, etc.
   string user_agent_family = 4;
 
@@ -76,6 +76,15 @@ message Access {
   // authorities are present, they are guaranteed to be sorted based on the
   // original ordering of the identity delegation events.
   repeated ServiceAccountDelegationInfo service_account_delegation_info = 9;
+
+  // A string that represents the username of a user, user account, or other
+  // entity involved in the access event. What the entity is and what its role
+  // in the access event is depends on the finding that this field appears in.
+  // The entity is likely not an IAM principal, but could be a user that is
+  // logged into an operating system, if the finding is VM-related, or a user
+  // that is logged into some type of application that is involved in the
+  // access event.
+  string user_name = 11;
 }
 
 // Identity delegation history of an authenticated service account.
@@ -97,4 +106,4 @@ message ServiceAccountDelegationInfo {
 message Geolocation {
   // A CLDR.
   string region_code = 1;
-}
+}