vatPercentage should support decimals

[JanMkl]

Describe the bug

vatPercentage is defined in the API documentation to be an integer. Snippet from the OpenAPI3 documentation:
vatPercentage:
type: integer
format: int64
example: 24
minimum: 0
maximum: 100
description: Item VAT percentage

Steps to Reproduce

Set a float and validate against the OpenAPI definition a type error produced.

Expected behaviour

The type should allow floats or other type of decimal numbers.

Actual behaviour

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Screenshots

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Additional context

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[atrotossavainen]

See #28