Policy for format updates

[ivirshup]

Please describe your wishes and possible alternatives to achieve the desired result.

We should create a policy to minimize disruption for format updates

[flying-sheep]

Current plan for nullable strings: #679 (comment)

We want opt-in writing so people don’t accidentally write files that can’t be read by most people.

So we’d add a setting that enables writing pd.StringDtype series, and if one of them is encountered without the setting being active, we throw an error that explains how to enable it and why it’s disabled by default.