Browse papertrail changes without object_changes

If you are using [PaperTrail](https://github.com/paper-trail-gem/paper_trail) to track changes to your data, but are not storing individual changesets, you can still see what changed from version to version using the snippet below:

```ruby
def hash_diff(from, to)
  from
  .dup
  .delete_if { |k, v| to[k] == v }
  .merge!(to.dup.delete_if { |k, v| from.key?(k) })
end

def present_diff(from_diff, to_diff)
  [].tap do |arr|
    arr << "FROM: #{from_diff}"   if from_diff.present?
    arr << "TO:   #{to_diff}\n\n" if to_diff.present?
  end
end

def list_papertrail_changes_for(obj)
  obj.versions.each_with_index.flat_map do |ver, idx|
    next if ver.object.nil?

    this_ver     = YAML.load(ver.object)
    next_version = obj.versions[idx + 1] || ver
    next_ver     = YAML.load(next_version.object)

    from_diff = hash_diff(this_ver, next_ver)
    to_diff   = hash_diff(next_ver, this_ver)

    present_diff(from_diff, to_diff)
  end.compact
end

puts list_papertrail_changes_for(thing)

FROM: {"ip_address"=>"", "updated_at"=>"2021-04-06T07:32:26.432Z"}
TO:   {"ip_address"=>"10.27.57.194", "updated_at"=>"2021-04-06T08:14:03.506Z"}

FROM: {"ip_address"=>"10.27.57.194", "updated_at"=>"2021-04-06T08:14:03.506Z"}
TO:   {"ip_address"=>"", "updated_at"=>"2021-04-09T13:47:07.485Z"}
```

gabrielfortuna
April 20, 2021