Doing an upsert on existing value, composite field not updated properly.
```
Input: {
id: "08ca34fe-fc39-474f-adac-4d89f844e922",
name: "tom",
linkedinLink: {
primaryLinkUrl: "https://www.linkedin.com/in/etienneyaouni1982",
primaryLinkLabel: "etienne",
secondaryLinks: null,
},
}
```
Building `overwrites` for upsert forgets `linkedinLink` because column
names are not flattened yet.
We don't want to call formatData yet on the input, because this is
heavy.
Overriding `overwrites` on execute.
