chore: Add migration to set the default empty string value for contact name (#7052)

Fixes: https://linear.app/chatwoot/issue/CW-1650/issue-with-the-contact-name

app/models/contact.rb

@@ -8,7 +8,7 @@
 #  email                 :string
 #  identifier            :string
 #  last_activity_at      :datetime
-#  name                  :string
+#  name                  :string           default("")
 #  phone_number          :string
 #  created_at            :datetime         not null
 #  updated_at            :datetime         not null

db/migrate/20230510113208_set_default_empty_string_for_contact_name.rb

@@ -0,0 +1,5 @@
+class SetDefaultEmptyStringForContactName < ActiveRecord::Migration[7.0]
+  def change
+    change_column_default :contacts, :name, from: nil, to: ''
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[7.0].define(version: 2023_05_10_060828) do
+ActiveRecord::Schema[7.0].define(version: 2023_05_10_113208) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "pg_stat_statements"
   enable_extension "pg_trgm"
@@ -394,7 +394,7 @@ ActiveRecord::Schema[7.0].define(version: 2023_05_10_060828) do
   end
 
   create_table "contacts", id: :serial, force: :cascade do |t|
-    t.string "name"
+    t.string "name", default: ""
     t.string "email"
     t.string "phone_number"
     t.integer "account_id", null: false