v3: Improve error when multiple timestamps are given w/operator

Previously, we were giving an error like `has an invalid timestamp
format. Timestamps should be formatted as 'YYYY-MM-DDThh:mm:ssZ'`. Now,
we detect that you are giving multiple comma-separated values and give
an error like `only accepts one value when using an inequality filter`.

[finishes #173575312]
Co-authored-by: Reid Mitchell <rmitchell@pivotal.io>
Co-authored-by: Teal Stannard <tstannard@pivotal.io>

Author: reidmit

app/messages/events_list_message.rb

@@ -27,6 +27,11 @@ def validate(record)
                 record.errors[:created_ats] << "Invalid comparison operator: '#{comparison_operator}'"
               end
 
+              if timestamp.to_s.include?(',')
+                record.errors[:created_ats] << 'only accepts one value when using an inequality filter'
+                next
+              end
+
               opinionated_iso_8601(timestamp, record)
             end
           end

spec/unit/messages/events_list_message_spec.rb

@@ -128,6 +128,12 @@ module VCAP::CloudController
             expect(message).to be_valid
           end
 
+          it 'does not allow multiple timestamps with an operator' do
+            message = EventsListMessage.from_params({ created_ats: { gte: "#{Time.now.utc.iso8601},#{Time.now.utc.iso8601}" } })
+            expect(message).not_to be_valid
+            expect(message.errors[:created_ats]).to include('only accepts one value when using an inequality filter')
+          end
+
           context 'when the operator is an equals operator' do
             it 'allows the equals operator' do
               message = EventsListMessage.from_params({ 'created_ats' => Time.now.utc.iso8601 })