add form events api

app/controllers/api/form_events_controller.rb

@@ -0,0 +1,35 @@
+# frozen_string_literal: true
+
+module Api
+  class FormEventsController < ApiBaseController
+    load_and_authorize_resource :submitter, parent: false
+
+    def index
+      submitters = @submitters.where.not(completed_at: nil)
+
+      params[:after] = Time.zone.at(params[:after].to_i) if params[:after].present?
+      params[:before] = Time.zone.at(params[:before].to_i) if params[:before].present?
+
+      submitters = paginate(
+        submitters.preload(template: :folder, submission: [:submitters, { audit_trail_attachment: :blob }],
+                           documents_attachments: :blob, attachments_attachments: :blob),
+        field: :completed_at
+      )
+
+      render json: {
+        data: submitters.map do |s|
+                {
+                  event_type: 'form.completed',
+                  timestamp: s.completed_at,
+                  data: Submitters::SerializeForWebhook.call(s)
+                }
+              end,
+        pagination: {
+          count: submitters.size,
+          next: submitters.last&.completed_at&.to_i,
+          prev: submitters.first&.completed_at&.to_i
+        }
+      }
+    end
+  end
+end