Add snapshot_on_deletion feature to AuditLog (#28)

### Summary

Because the `changes` hash is always empty on deletion, we would like the option to create a snapshot by default on deletes, to ensure that we know what it was exactly that was deleted. (This is particularly useful for models that existed prior to the introduction of this framework.)

### Other Information

I'm defaulting it to `false` because ... I guess it felt extra confusing to have a feature that defaults to only partially being enabled. But I could be convinced that `true` is actually a better default 🤷

.gitignore

@@ -3,6 +3,7 @@
 Gemfile.lock
 log/*.log
 pkg/
+spec/examples.txt
 spec/dummy/log/*.log
 spec/dummy/tmp/
 /gemfiles/*.gemfile.lock

README.md

@@ -345,6 +345,15 @@ Journaled::AuditLog.with_snapshots do
 end
 ```
 
+Snapshots can also be enabled globally for all _deletion_ operations. Since
+`changes` will be empty on deletion, you should consider using this if you care
+about the contents of any records being deleted (and/or don't have a full audit
+trail from their time of creation):
+
+```ruby
+Journaled::AuditLog.snapshot_on_deletion = true
+```
+
 Events with snapshots will continue to populate the `changes` field, but will
 additionally contain a snapshot with the full state of the user:
 

app/models/journaled/audit_log/event.rb

@@ -58,7 +58,8 @@ def changes
       end
 
       def snapshot
-        filtered_attributes if record._log_snapshot || AuditLog.snapshots_enabled
+        filtered_attributes if record._log_snapshot || AuditLog.snapshots_enabled ||
+          (database_operation == 'delete' && AuditLog.snapshot_on_deletion)
       end
 
       def actor

lib/journaled/audit_log.rb

@@ -18,6 +18,7 @@ module AuditLog
     mattr_accessor(:default_enqueue_opts) { {} }
     mattr_accessor(:excluded_classes) { DEFAULT_EXCLUDED_CLASSES.dup }
     thread_mattr_accessor(:snapshots_enabled) { false }
+    thread_mattr_accessor(:snapshot_on_deletion) { false }
     thread_mattr_accessor(:_disabled) { false }
     thread_mattr_accessor(:_force) { false }
 

lib/journaled/version.rb

@@ -1,3 +1,3 @@
 module Journaled
-  VERSION = "5.1.1".freeze
+  VERSION = "5.2.0".freeze
 end

spec/lib/journaled/audit_log_spec.rb

@@ -389,6 +389,23 @@ def assign_attrs(**attrs)
           end
         end
       end
+
+      context 'and snapshotting is enabled only on deletion' do
+        subject { MyModel.new(name: 'bob') }
+
+        before do
+          described_class.snapshot_on_deletion = true
+        end
+
+        it 'emits snapshots through the lifecycle of the object, and filters the expected fields' do
+          expect { subject.save }
+            .to not_journal_event_including(snapshot: { all: 'attributes', password: '[FILTERED]' })
+          expect { subject.update(name: 'robert') }
+            .to not_journal_event_including(snapshot: { all: 'attributes', password: '[FILTERED]' })
+          expect { subject.destroy }
+            .to journal_event_including(snapshot: { all: 'attributes', password: '[FILTERED]' })
+        end
+      end
     end
 
     context 'and a field is ignored' do

spec/spec_helper.rb

@@ -24,6 +24,7 @@
     mocks.verify_partial_doubles = true
   end
 
+  config.example_status_persistence_file_path = 'spec/examples.txt'
   config.order = :random
 end