add is first to completed submitters

app/models/completed_submitter.rb

@@ -6,6 +6,7 @@
 #
 #  id                  :bigint           not null, primary key
 #  completed_at        :datetime         not null
+#  is_first            :boolean
 #  sms_count           :integer          not null
 #  source              :string           not null
 #  verification_method :string
@@ -18,8 +19,10 @@
 #
 # Indexes
 #
-#  index_completed_submitters_on_account_id    (account_id)
-#  index_completed_submitters_on_submitter_id  (submitter_id) UNIQUE
+#  index_completed_submitters_on_account_id                   (account_id)
+#  index_completed_submitters_on_account_id_and_completed_at  (account_id,completed_at) WHERE (is_first = true)
+#  index_completed_submitters_on_submission_id                (submission_id) UNIQUE WHERE (is_first = true)
+#  index_completed_submitters_on_submitter_id                 (submitter_id) UNIQUE
 #
 class CompletedSubmitter < ApplicationRecord
   belongs_to :submitter