Add database support and model for tips

app/models/tip.rb

@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+class Tip < ApplicationRecord
+  include Creation
+
+  has_many :exercise_tips
+  has_many :exercises, through: :exercise_tips
+  belongs_to :file_type, optional: true
+  validates_presence_of :file_type, if: :example?
+  validate :content?
+
+  def content?
+    errors.add :description, I18n.t('activerecord.errors.messages.at_least', attribute: I18n.t('activerecord.attributes.tip.example')) unless [description?, example?].include?(true)
+  end
+
+  def to_s
+    if title?
+      "#{I18n.t('activerecord.models.tip.one')}: #{title} (#{id})"
+    else
+      "#{I18n.t('activerecord.models.tip.one')} #{id}"
+    end
+  end
+end