Allow user to specify an attribute as a primary key.

[github-actions]

Requires either changing default primary key or using secondary index

rethinkdb-orm/src/rethinkdb-orm/persistence.cr

Line 217 in 44eff6a

# TODO: Allow user to specify an attribute as a primary key.

      run_save_callbacks do
        raise RethinkORM::Error::DocumentInvalid.new(self) unless valid?

        # TODO: Allow user to specify an attribute as a primary key.
        # Requires either changing default primary key or using secondary index
        @id = @@uuid_generator.next(self) if @id.presence.nil?

        response = Connection.raw_json(self.to_json) do |q, doc|