Specify table name in obfuscate calls

As of today, we just blindly try to match a global list of fields we want to be obfuscated against all the attributes of every row Polo traverses:

polo/lib/polo/translator.rb

Line 38 in b79e48e

next if intersection(instance.attributes.keys, fields).empty?

To do so, we pass in a list of fields to Polo.configure

Polo.configure do
  obfuscate :email
end

While this has been working well, it could be the case that someone wants to only obfuscate certain fields in certain tables.

What I'm suggesting is that we change the obfuscate method to also accept something like this:

Polo.configure do
  obfuscate "users.email" 
end

So in this case we're only obfuscating email fields in the users table, and not obfuscating emails on some other tables such as invites or some other table where emails are not sensitive.

What do you think, @danielvlopes?

How about

Polo.configure do
  email_scrubber = ->(e) { # secret stuff }
  pure_nonsense = -> (v) { # make nonsense }
  obfuscate users: { email: email_scrubber },
                   credit_cards: { number: pure_nonsense}
end

or something like that

This looks even better. Though I think this would break the existing api.

I needed this feature so I made this #30

Solved by #30