chore: Add Index for widget contact lookup (#6998)

- Adds an index to improve the contact lookup performance while calling setUser from widget

app/models/contact.rb

@@ -17,6 +17,7 @@
 # Indexes
 #
 #  index_contacts_on_account_id                          (account_id)
+#  index_contacts_on_lower_email_account_id              (lower((email)::text), account_id)
 #  index_contacts_on_name_email_phone_number_identifier  (name,email,phone_number,identifier) USING gin
 #  index_contacts_on_phone_number_and_account_id         (phone_number,account_id)
 #  uniq_email_per_account_contact                        (email,account_id) UNIQUE

db/migrate/20230426130150_add_index_for_widget_contact_look_up.rb

@@ -0,0 +1,7 @@
+class AddIndexForWidgetContactLookUp < ActiveRecord::Migration[6.1]
+  disable_ddl_transaction!
+
+  def change
+    add_index :contacts, 'LOWER(email), account_id', name: 'index_contacts_on_lower_email_account_id', algorithm: :concurrently
+  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.define(version: 2023_04_18_100944) do
+ActiveRecord::Schema.define(version: 2023_04_26_130150) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "pg_stat_statements"
@@ -405,6 +405,7 @@ ActiveRecord::Schema.define(version: 2023_04_18_100944) do
     t.string "identifier"
     t.jsonb "custom_attributes", default: {}
     t.datetime "last_activity_at"
+    t.index "lower((email)::text), account_id", name: "index_contacts_on_lower_email_account_id"
     t.index ["account_id"], name: "index_contacts_on_account_id"
     t.index ["email", "account_id"], name: "uniq_email_per_account_contact", unique: true
     t.index ["identifier", "account_id"], name: "uniq_identifier_per_account_contact", unique: true