Complex types diffs

[palkan]

Related to #30

The problem

The log doesn't respect complex data types such as jsonb, array, hstore, etc (due to the usage of hstore under the hood. The values for these types are just strings.

We have to manually cast them back to appropriate Ruby structure.

Example:

post = Post.create!(tags: ['some', 'tag']) # tags is an array column

post.udpate!(tags: ['other'])

post.reload.diff_from(...)
#=> {"old"=>{"tags"=>["some", "tag"]}, "new"=>"{\"tags\": [\"other\"]}"}

# but should be

#=> {"old"=>{"tags"=>["some", "tag"]}, "new"=>{"tags"=>["other"]}}

The problem also may affect the at methods.

[jcsrb]

the information can be found inside the model like this

Post.column_for_attribute('tags').type

and based on that additional casting can be added