created channel for action cable and friendship relationship in database

db/migrate/20180827151325_create_connections.rb

@@ -0,0 +1,8 @@
+class CreateConnections < ActiveRecord::Migration[5.2]
+  def change
+    create_table :connections do |t|
+      t.references :user, foreign_key: true, index: true
+      t.references :contact, foreign_key: { to_table: :users }, index: true
+    end
+  end
+end