[Feature]: Change money amounts from float to decimal types

[Pandorax100]

What problem are you trying to solve?

Currently all money amounts are floating points (floats). They should be decimal types because decimal provides exact base-10 precision, which is required for financial calculations. Floating-point types (float and double) store values in binary, meaning many decimal fractions (such as 0.1) cannot be represented exactly. The decimal type is specifically designed for working with currency values.

Proposed solution

Update the 'format' property of the Sumup Open API spec to 'decimal' for money properties to allow consumers to generate proper currency safe types.
An example: https://github.com/sumup/sumup-openapi/blob/754237a94d8badea0f7e209c977b94cc95347f05/openapi.json#L5792

The format property is an open string property, can have any value, and it is up to generators to consume the 'format' property.
https://github.com/OAI/OpenAPI-Specification/blob/main/versions/2.0.md#data-types

Alternatives considered

Alternatives I have considered is changing the generator.go with a workaround to determine what properties should be decimal. If the SumUp Open API spec cannot be changed perhaps we could have a way to determine which properties should be decimal around the "number" section of the genrator.

sumup-dotnet/codegen/internal/generator/generator.go

Line 1395 in b238fb3

case schemaHasType(schema, "number"):

Use case

This would help financial values keep their precision and avoid floating point rounding errors.

Additional context

No response

[matoous]

Hi @Pandorax100, thanks for the report. We are aware of this issue and all new endpoints (such as checkout for card readers) already use minor units. We can't unfortunately update existing APIs without breaking contract for existing integrations. We are working on a new set of APIs that will all be using minor units until then, I am afraid we don't have many options.