Add CacheCrispies::Base#transform_keys method

[wujibear]

I was asking about being able to transform keys to something like camelcase and tried this out.
Unsure of your needs for contributions, but let me know what you think of the idea.

With this I can now do the following:

# app/serializers/rest/v1_serializer.rb
class Rest::V1Serializer < CacheCrispies::Base
  transform_keys lambda { |key| key.to_s.camelize(:lower) }
end

# app/serializers/rest/v1/some_serializer.rb
class Rest::V1::SomeSerializer < Rest::V1Serializer
  serialize :id, :created_at, :some_thing
end

Serialized data will look like:

{
  "id": "123",
  "createdAt": "date",
  "someThing": "here"
}

I then have all my serializers inherit from this one and now all my keys will be transformed to lower camelcase

See: #52

[wujibear]

Actually, this only seems to work if I put the method in the serializer that is serializing.
Doesn't seem to get inherited for some reason, investigating that.

[wujibear]

K. Fixed that, now it checks for parent definitions if no proc or existing instance var is supplied.
This lets you write a pattern you can inherit from, but any serializer can explicitly set its own transform method for its attributes

[adamcrown]

Thanks for the PR. This seems reasonable. I know JS tends to lean towards snake-cased variables and having the JSON the same way can make things simpler with object deconstruction.

I would want to see some specs to cover this new functionality before I would merge it though.

[wujibear]

Any other thoughts on method naming, or implementation though?

[wujibear]

Added a spec and docs

[wujibear]

@adamcrown got those specs for you

[wujibear]

@adamcrown Any other thoughts?
Would you want to merge this?

[adamcrown]

I think this is looking really good. I do have a couple small questions though. And apologies for the wait in getting back on this. I should have more time to keep up with this gem now for multiple reasons. So I should be able to come back to this PR soon soon after these comments are addressed.

[adamcrown]

Why is the || attrib needed here?

[wujibear]

I'm not great at seeing GH notifications, sorry.
I plan to check out your comments here and address in the next week or two.

I'll need to get back in the code here to recall correctly, but I believe this was meant as an improvement.
It seems like it calls for adding a comment to explain why, lol

[adamcrown]

Could we use a block here rather than a lambda argument?

It just reads a bit better and is a bit more consistent to me to have

transform_keys lambda { |key| key.to_s.camelize(:lower) }

[wujibear]

It looks like you just repeated the line I have there... accident yes?
You're meaning to have something like this instead?

transform_keys do |key|
  key.to_s.camelize(:lower)
end