[feature] add option to disable converting ISO strings to dates

[chrisradek]

This adds a new load option - disableAutoISOConversions. This turns off the automatic conversion of event fields where any strings that appear as an ISO8601 string (including just dates, e.g. YYYY-MM-DD) become Date objects.

Background

Through @segment/facade, any events passed to classic integrations had any ISO strings converted to Dates. I suspect this was intentional behavior because the way we cloned events (JSON.parse(JSON.stringify(event))) converted Dates to ISO8601 strings, so facade was converting them back to dates.

However, some users want their ISO strings to be passed to integrations as is, especially when the string represents a calendar date and not a time.

PR details

@segment/facade supports turning off this conversion by setting traverse to false, so the new option ultimately sets the traverse flag.

I also changed how we clone events so that users can still specify a property as a Date object and have that carried over to the cloned event regardless of the new setting. It looks like analytics.js classic also did a deep clone of the event instead of our JSON.parse(JSON.stringify(event)) trick, so this shouldn't cause any unintended consequences.

I made this field default to false, meaning users need to opt-in to this new behavior. I made it opt-in to prevent potentially impacting user-defined destination middleware.

[x] I've included a changeset (psst. run yarn changeset. Read about changesets here).

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🦋 Changeset detected

Latest commit: 88cb9c2

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@segment/analytics-next	Minor

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[silesky]

Very happy to get rid of JSON.parse(JSON.stringify(event))! That's a pretty worrying / destructive operation in general.