Introduce JSON::Coder

[etiennebarrie]

Since #to_json methods are global, it can sometimes be problematic if you need a given type to be
serialized in different ways in different locations.

Instead it is recommended to use the newer JSON::Coder API:

module MyApp
  API_JSON_CODER = JSON::Coder.new do |object|
    case object
    when Time
      object.iso8601(3)
    else
      object
    end
  end
end

puts MyApp::API_JSON_CODER.dump(Time.now.utc) # => "2025-01-21T08:41:44.286Z"

The provided block is called for all objects that don't have a native JSON equivalent, and
must return a Ruby object that has a native JSON equivalent.

[paddor]

I love this. That's exactly what I'd need to make sure my Time objects are encoded as ISO8601 with millisecond precision without monkey patching.

Doing this just doesn't feel right:

class Time
  def to_json(*a)
    iso8601(3).to_json(*a)
  end
end

So far I've been relying on Oj's time_format: :xmlschema, second_precision: 3.