Add custom census authorization handler

[fblupi]

This authorization handler allows users to be directly verified with their birthdates by checking the records in a table.

You need to create records for the model Decidim::CustomCensusRecord. For example:

[
  { email: "[email protected]", date_of_birth: "1956-03-14" },
  { email: "[email protected]", date_of_birth: "1998-12-06" }
].each do |record|
  Decidim::CustomCensusRecord.create(email: record[:email], metadata: { date_of_birth: record[:date_of_birth] })
end

The verification will succeed if the user is in the census and introduces the same birthdate as the one in the database.

This authorization handler will allow us to work with the Decidim Kids module.