Add reported_by tag to error backend errors

.changesets/add--reported_by--tag-to-errors-reported-by-the-legacy-error-backend.md

@@ -0,0 +1,6 @@
+---
+bump: patch
+type: add
+---
+
+Add `reported_by` tag to errors reported by the legacy error backend. This makes it easier to understand whether an error is being reported by the error backend.

lib/appsignal/error/backend.ex

@@ -90,6 +90,7 @@ defmodule Appsignal.Error.Backend do
   defp set_error_data(span, reason, stacktrace) do
     span
     |> @span.add_error(:error, reason, stacktrace)
+    |> @span.set_sample_data("tags", %{"reported_by" => "error_backend"})
     |> @tracer.close_span()
   end
 end

test/appsignal/error/backend_test.exs

@@ -225,6 +225,11 @@ defmodule Appsignal.Error.BackendTest do
       assert is_list(stack)
     end
 
+    test "adds a `reported_by` tag to the created span", %{pid: pid} do
+      assert {:ok, [{%Span{pid: ^pid}, "tags", %{"reported_by" => "error_backend"}} | _]} =
+               Test.Span.get(:set_sample_data)
+    end
+
     test "closes the created span", %{pid: pid} do
       assert {:ok, [{%Span{pid: ^pid}} | _]} = Test.Tracer.get(:close_span)
     end