Non-required attributes are not automatically generated to have `| null` appended to type

[mkmckenzie]

The documentation states:

Non-required attributes automatically have | null appended to their type.

However after generating types, there is not a single instance of null in the generated files, despite dozens of attributes being non-required.

Node version: 16.17.0
Package version: 3.4.0

Yarn script:

yarn contentful-typescript-codegen --output src/types/contentful/types.generated.ts --fieldsOnly && contentful-typescript-codegen --output server/types/contentful/types.generated.ts --fieldsOnly

Expected output:

      /** Add To Bag Text */
    addToBagText?: string | null;

    /** Bag Text */
    bagText?: string | null;

    /** Added To Bag Text */
    addedToBagText?: string | null;

Actual output:

      /** Add To Bag Text */
    addToBagText?: string | undefined;

    /** Bag Text */
    bagText?: string | undefined;

    /** Added To Bag Text */
    addedToBagText?: string | undefined;

Any debugging guidance would be greatly appreciated! Thank you!