Optimize database SQL queries using GraphQL::Execution::Lookahead

**What is lookahead?**
https://graphql-ruby.org/queries/lookahead.html#getting-a-lookahead

**How we can implement it?**
In the example below `recent_assessments` association will be loaded if `can_make_assessment` will be selected in GraphQL request.
```ruby
# app/graphql/resolvers/base.rb
module Resolvers
class Base < GraphQL::Schema::Resolver
include ActionPolicy::GraphQL::Behaviour

argument_class Types::BaseArgument

def resolve(**options)
@options = options
fetch_data
end

private

attr_reader :options

def fetch_data
raise NotImplementedError
end

def current_user
@current_user ||= context[:current_user]
end

def preload_associations
lookahead_selection_names.each_with_object([]) do |selection, associations|
associations << self.class::PRELOAD_ASSOCIATIONS_MAPPING[selection]
end.flatten.compact
end

def lookahead_selection_names
options[:lookahead].selections.map { |s| s.name.to_sym }
end
end
end

# app/graphql/resolvers/users.rb
module Resolvers
class Users < Resolvers::Base
# some arguments

extras [:lookahead]

type [Types::UserType], null: true

PRELOAD_ASSOCIATIONS_MAPPING = {
can_make_assessment: [:recent_assessments]
}.freeze

def fetch_data
sorted_relation(filtered_relation)
end

private

def filtered_relation
FilteredUsersQuery.new(relation, options).all
end

def relation
object.users.includes(preload_associations)
end
end
end
```