personalize-events client sentAt parameter type

[seashman]

I noticed the sentAt parameter for an Event in the personalize-events client accepts only Date type. It used to accept multiple types in version 2 of the sdk. Is this correct? The API docs state the type is a timestamp, so customers would expect to be able to pass a timestamp in addition to a Date type. If they use Date, they have to convert the timestamp. Customers upgrading to v3 might be frustrated with the "Error TypeError: input.sentAt.getTime is not a function" error they receive when they pass a timestamp instead of a Date.

I think extra validation can be added to line 356 in aws-sdk-js-v3/clients/client-personalize-events/src/protocols/Aws_restJson1.ts. to accept a unix timestamp (ie convert the timestamp to a Date here rather than making customers do it).

client: personalize-events
sentAt is defined on line 60 in aws-sdk-js-v3/clients/client-personalize-events/src/models/models_0.ts
Validation is done on line 356 in aws-sdk-js-v3/clients/client-personalize-events/src/protocols/Aws_restJson1.ts.
sentAt param in V3 docs: https://docs.aws.amazon.com/AWSJavaScriptSDK/v3/latest/clients/client-personalize-events/modules/event.html.
sentAt param in V2 docs: https://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/PersonalizeEvents.html#putEvents-property
Amazon Personalize API: States it is a timestamp at https://docs.aws.amazon.com/personalize/latest/dg/API_UBS_Event.html