DEV: Fix `FakeLogger` spec issues (#12397)

* DEV: Add `#level` and `#level=` to `FakeLogger`

* DEV: Fix a leaky test

spec/models/theme_spec.rb

@@ -657,7 +657,10 @@ HTML
     end
 
     it 'warns when the theme has modified the setting type but data cannot be converted' do
+      begin
+        @orig_logger = Rails.logger
         Rails.logger = FakeLogger.new
+
         theme.set_field(target: :settings, name: :yaml, value: "valid_json_schema_setting:\n  default: \"\"\n  type: \"list\"")
         theme.save!
 
@@ -671,6 +674,9 @@ HTML
         theme.convert_settings
         expect(setting.value).to eq("red,globe")
         expect(Rails.logger.warnings[0]).to include("Theme setting type has changed but cannot be converted.")
+      ensure
+        Rails.logger = @orig_logger
+      end
     end
   end
 

spec/support/fake_logger.rb

@@ -2,6 +2,7 @@
 
 class FakeLogger
   attr_reader :warnings, :errors, :infos, :fatals
+  attr_accessor :level
 
   def initialize
     @warnings = []