2.7.0 :033 > user4.contact_request(user5)
  Connection Exists? (0.3ms)  SELECT 1 AS one FROM "connections" WHERE "connections"."user_id" = ? AND "connections"."contact_id" = ? LIMIT ?  [["user_id", 7], ["contact_id", 8], ["LIMIT", 1]]
  TRANSACTION (0.1ms)  begin transaction
  Connection Create (1.1ms)  INSERT INTO "connections" ("user_id", "contact_id", "created_at", "updated_at") VALUES (?, ?, ?, ?)  [["user_id", 7], ["contact_id", 8], ["created_at", "2021-04-19 23:45:32.553041"], ["updated_at", "2021-04-19 23:45:32.553041"]]
  TRANSACTION (0.1ms)  rollback transaction
Traceback (most recent call last):
        4: from (irb):32
        3: from (irb):33:in `rescue in irb_binding'
        2: from app/models/user.rb:49:in `contact_request'
        1: from app/models/user.rb:50:in `block in contact_request'
ActiveRecord::StatementInvalid (SQLite3::SQLException: no such table: main.contacts)

class User < ApplicationRecord
  # Include default devise modules. Others available are:
  # :confirmable, :lockable, :timeoutable, :trackable and :omniauthable
  devise :database_authenticatable, :registerable,
         :recoverable, :rememberable, :validatable
	has_many :developments, dependent: :destroy
	has_many :connections
	has_many :connections, dependent: :destroy
	has_many :contacts, -> { where connections: { status: :accepted }}, through: :connections
	has_many :requested_contacts, -> { where connections: {status: :requested}}, through: :connections, source: :contact
	has_many :pending_contacts, -> { where connections: { status: :pending }}, through: :connections, source: :contact	
        has_many :blocked_contacts, -> { where connections: { status: :blocked }}, through: :connections, source: :contact

class Connection < ApplicationRecord
  belongs_to :user
  belongs_to :contact, class_name: 'User'
  enum status: {pending: 0, requested: 1, accepted: 2, blocked: 3}
  # id: 1
  # contact: 2

  # user_id: 1, contact_id: 2, status: :requested
  # user_id: 2, contact_id: 1, status: :pending
end

def contact_request(contact)
		unless self == contact || Connection.where(user: self, contact: contact).exists?
			transaction do
			Connection.create(user: self, contact: contact, status: :pending)
			Connection.create(user: contact, contact: self, status: :requested)
			end
		end
	end

	def accept_request(contact)
		transaction do
			Connection.find_by(user: self, contact: contact, status: [:requested])&.accepted!
			Connection.find_by(user: contact, contact: self, status: [:pending])&.accepted!
		end
	end