Add support for generating a Set for a list with uniqueItems set to true

[marcdejonge]

To fix #9848

This specifically adds support for a Set type when a model with an array has uniqueItems set to true. This only changes the KotlinClientGenerator template, since that one was missing specific support for it. The tests run agains all 5 generators, but the rest seem to work fine.

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[marcdejonge]

@jimschubert @dr4ke616 @karismann @Zomzog @andrewemery @4brunu @yutaka0m

Is this the correct solution? I'd much rather go back to the {{{dataType}}} solution, but then it would break the kotlinx-serializer I think.

[4brunu]

Instead of changing the template, what about changing the java file?
#6773
Here is an example of something similar in the swift client.

[marcdejonge]

Instead of changing the template, what about changing the java file?
#6773
Here is an example of something similar in the swift client.

I agree, but the template already doesn't use the dataType at all. The code already contains the logic for using a Set instead of a List (for the kotlin server templates it works fine). I don't know how else to solve this.

[4brunu]

Thanks, let's go with this solution 👍