business_category.rb

class BusinessCategory < ApplicationRecord
  validates_presence_of :name
  has_many :jobs
  has_many :business_industries, through: :jobs
end

business_industry.rb

class BusinessIndustry < ActiveRecord::Base
  belongs_to :business_category
  validates_presence_of :name
  has_many :jobs
  has_many :business_categories, through: :jobs
end

job.rb

class Job < ApplicationRecord
  belongs_to :user
  belongs_to :business_information
  belongs_to :business_category
  belongs_to :business_industry
end

user.rb

class User < ApplicationRecord
  belongs_to :team
  has_secure_password

  has_one :membership_payment
  has_one :membership_application

  has_one :job
  accepts_nested_attributes_for :job

  validates_presence_of :email
  validates_presence_of :phone_number
  validates_presence_of :first_name
  validates_presence_of :last_name
  validates_presence_of :birthday
  validates_presence_of :role
end