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

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

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