Object keys with numbers do not format correctly by default

[shadowhand]

The default key formatter uses the regex pattern /(.)(?=[A-Z])/u.

This regex pattern does not properly handle key names like procedureModifier1 which I would expect to formats to/from procedure_modifier_1. It currently translates formats to/from procedure_modifier1.

Changing the regex to /(.)(?=[A-Z0-9])/u corrects the formatting.

[shadowhand]

This is purely a matter of preference. In fact, using a custom formatter in a project created another bug where it was not expected to have the underscore before a number. 🤦🏼‍♂️