app/models/sponsor.rb
class Sponsor < ApplicationRecord
MINIMUM_AMOUNT_VALUE = 0
belongs_to :cat
belongs_to :user
validates :start_date, presence: true
validates :last_payment_date, presence: true
validates :amount, presence: true
validates_inclusion_of :renovate, in: [true, false]
validates :amount, numericality: {greater_than: MINIMUM_AMOUNT_VALUE}
validates_with SponsorValidator
end