Pass down SignedUserName down to AccessLogger context (#16605) (#16616)

Backport #16605

Unfortunately when the AccessLogger was moved back before the contexters the
SignedUserName reporting was lost. This is due to Request.WithContext leading to a
shallow copy of the Request and the modules/context/Context being within that request.

This PR adds a new context variable of a string pointer which is set and handled
in the contexters.

Fix #16600

Signed-off-by: Andrew Thornton <art27@cantab.net>

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

modules/context/api.go

@@ -275,6 +275,17 @@ func APIContexter() func(http.Handler) http.Handler {
 			ctx.Data["CsrfToken"] = html.EscapeString(ctx.csrf.GetToken())
 
 			next.ServeHTTP(ctx.Resp, ctx.Req)
+
+			// Handle adding signedUserName to the context for the AccessLogger
+			usernameInterface := ctx.Data["SignedUserName"]
+			identityPtrInterface := ctx.Req.Context().Value(signedUserNameStringPointerKey)
+			if usernameInterface != nil && identityPtrInterface != nil {
+				username := usernameInterface.(string)
+				identityPtr := identityPtrInterface.(*string)
+				if identityPtr != nil && username != "" {
+					*identityPtr = username
+				}
+			}
 		})
 	}
 }