Bugfix: Use server timestamp to set agent_last_seen_at (#1114)

spec/controllers/api/v1/accounts/conversations_controller_spec.rb

@@ -177,15 +177,12 @@ RSpec.describe 'Conversations API', type: :request do
       let(:agent) { create(:user, account: account, role: :agent) }
 
       it 'updates last seen' do
-        params = { agent_last_seen_at: '-1' }
-
         post "/api/v1/accounts/#{account.id}/conversations/#{conversation.display_id}/update_last_seen",
              headers: agent.create_new_auth_token,
-             params: params,
              as: :json
 
         expect(response).to have_http_status(:success)
-        expect(conversation.reload.agent_last_seen_at).to eq(DateTime.strptime(params[:agent_last_seen_at].to_s, '%s'))
+        expect(conversation.reload.agent_last_seen_at).not_to eq nil
       end
     end
   end