fix: make fixup script consistent with migration docs

[cguardia]

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Fixes#199🦕

The following changes to the fixup script are part of the PR:

• Generate code consistent with the upgrade documentation.
• Add an option to generate the code using keyword arguments instead of a request.
• Generate stylistically consistent code (no spaces in keywords, double quotes for strings).
• Reformat the script itself to use the same code styling.

[anguillanneuf]

Thank you for this PR.