【WIP】Add each_serializer option support to CollectionSerializer

[tashirosota]

Purpose

• Raise ArgumentError "Cannot infer..." when collection is empty -v 10.0.7
• issues: Raise ArgumentError "Cannot infer root key from collection type. Please specify the root or each_serializer option, or render a JSON String" when collection is empty array in >= 10.0.7 #2406

Changes

• lib/active_model/serializer/collection_serializer.rb :43 add check to each_serializer option

Related GitHub issues

• Raise ArgumentError "Cannot infer root key from collection type. Please specify the root or each_serializer option, or render a JSON String" when collection is empty array in >= 10.0.7 #2406

Additional helpful information

• Our production project has passed all rspec by this patch

[tashirosota]

Serializer class is singular most of the time.