Add a error logger exception handler

lib/alchemy/error_tracking.rb

@@ -9,6 +9,8 @@ def self.call(exception)
     end
 
     mattr_accessor :notification_handler
-    @@notification_handler = BaseHandler
   end
 end
+
+require "alchemy/error_tracking/error_logger"
+Alchemy::ErrorTracking.notification_handler = Alchemy::ErrorTracking::ErrorLogger

lib/alchemy/error_tracking/error_logger.rb

@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+module Alchemy
+  module ErrorTracking
+    class ErrorLogger < BaseHandler
+      def self.call(exception)
+        ::Rails.logger.tagged("alchemy_cms") do
+          ::Rails.logger.error("#{exception.class.name}: #{exception.message} in #{exception.backtrace.first}")
+        end
+      end
+    end
+  end
+end

spec/libraries/alchemy/error_tracking/error_logger_spec.rb

@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+require "rails_helper"
+
+RSpec.describe Alchemy::ErrorTracking::ErrorLogger do
+  describe ".call" do
+    it "logs the exception into Rails logger with alchemy_cms tag" do
+      expect(::Rails.logger).to receive(:tagged).with("alchemy_cms").and_yield
+      expect(::Rails.logger).to receive(:error).with("RuntimeError: foo in /foo/bar.rb:1")
+      error = RuntimeError.new("foo")
+      error.set_backtrace(["/foo/bar.rb:1"])
+      described_class.call(error)
+    end
+  end
+end