Add Snippets bounded context

Why

#476169 (closed)

Snippets code needs to deepen with nestings like:

module Snippets
  module PersonalSnippets
    class BuildService < Snippets::BaseService
      def execute
        # ...
      end
    end
  end
end

Currently trying to add this class throws a LEFTHOOK error.

What

Add snippets as a bounded context.