Fix numbers autoincrement

app/models/check.rb

@@ -52,7 +52,9 @@ class Check < ApplicationRecord
                         :standard_text,
                         :powerpoint_text
 
-  after_create { update(number: id) unless number }
+  validates :number, uniqueness: true, presence: true
+
+  before_validation { self.number = self.class.maximum(:id).to_i + 1 unless self.number.present? }
 
   scope(:search, lambda { |term|
     # TODO: Search only fields for current locale.

app/views/checks/_form.html.slim

@@ -1,7 +1,7 @@
 = bootstrap_form_with(model: check, remote: true) do |form|
   h2 Details
   = multilang_form_field(form, :name)
-  = form.text_field :number
+  = form.text_field :number, required: false
   .row
     = form.collection_radio_buttons(:principle_id, Principle.all.sort_by(&:t_name), :id, :t_name) { |b| b.label(class: "col-md-2") { b.radio_button + b.text } }
   = form.collection_check_boxes :standard_ids, Standard.all.sort_by{ _1.t_name.downcase }, :id, :t_name, include_blank: true