Upsert should not modify passed in data object

[mpalmerlee]

Describe the bug

If I call upsert using a javascript object (not an entity) the upsert method modifies the passed in object. It looks like this is caused by this line:

ChangeSetPersister.mapReturnedValues

Reproduction

mpalmerlee/mikro-orm-reproduction@a3590ef

What driver are you using?

@mikro-orm/postgresql

MikroORM version

@mikro-orm/core@6.0.5-dev.1

Node.js version

v20.5.0

Operating system

OSX

Validations

• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
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• The provided reproduction is a minimal reproducible example of the bug.

[mpalmerlee]

Notice in the linked repro the data object now contains the id: