Serialize times with milliseconds

[josuemontano]

Describe the bug

Timestamps cannot be used to generate stable cursors since they are serialized with precision of seconds

https://github.com/bibendi/graphql-connections/blob/c979406fc407216384fbe80351c1cf749794eae8/lib/graphql/connections/base.rb#L42

To Reproduce

1. Install the graphql gem.
2. Create a User ActiveRecord model with timestamps, such as created_at.
3. Create a type for the User model
4. Create a query to fetch users which returns a stable connection from this gem

class User < ApplicationRecord
end

module Types
  class UserType < Types::BaseObject
    field :id, ID, null: false
  end
end

module Types
  class QueryType < Types::BaseObject
    field :users, Types::UserType.connection_type, null: false
    def users
      GraphQL::Connections::Stable.new(User.all, primary_key: :created_at)
    end
  end
end

The generated SQL looks like this:

SELECT "users".* FROM "users"
WHERE "users"."created_at" > '2021-11-10 14:26:19'
ORDER BY "users"."created_at" ASC LIMIT 10

Expected behavior
The SQL query should include milliseconds to avoid skipping records that were created in the same second:

SELECT "users".* FROM "users"
WHERE "users"."created_at" > '2021-11-10 14:26:19.152283'
ORDER BY "users"."created_at" ASC LIMIT 10

To achieve it, serialize times with higher precision

# lib/graphql/connections/base.rb
def serialize(cursor)
  case cursor
  when Time, DateTime, Date
    cursor.iso8601(9)
  else
    cursor.to_s
  end
end

Context (please complete the following information):

• Ruby: 2.7.4
• graphql gem: 1.14
• rails: 6.1

[bibendi]

Hi!
Makes sense!