Apply suggestions from code review

Co-authored-by: Andrea Leopardi <an.leopardi@gmail.com>

Author: solnic

lib/sentry/config.ex

@@ -79,7 +79,7 @@ defmodule Sentry.Config do
           """
         ],
         skip_error_report_callback: [
-          type: {:custom, __MODULE__, :__validate_skip_error_report_callback__, []},
+          type: {:or, [nil, {:fun, 2}]},
           default: nil,
           type_doc: "`(Oban.Worker.t() | nil, Oban.Job.t() -> boolean())` or `nil`",
           doc: """

lib/sentry/integrations/oban/error_reporter.ex

@@ -67,8 +67,12 @@ defmodule Sentry.Integrations.Oban.ErrorReporter do
     rescue
       error ->
         Logger.warning(
-          "skip_error_report_callback failed for worker #{inspect(worker)} " <>
-            "(job ID #{job.id}): #{inspect(error)}"
+          """
+          :skip_error_report_callback failed for worker #{inspect(worker)} \
+          (job ID #{job.id}):
+          
+          #{Exception.format(:error, error, __STACKTRACE__)}\
+          """
         )
 
         false