[kotlin] Add integration test for query params

[pkubowicz]

This is a test for a regression from #22512 where param values were written as a list.

The test passes when the change to ApiClient.kt is reverted. Fails on the regression:

Expected :/pet/findByStatus?status=pending,available
Actual   :/pet/findByStatus?status=%5Bpending%2Cavailable%5D

Expected :/user/login?username=myUsername&password=myPassword
Actual   :/user/login?username=%5BmyUsername%5D&password=%5BmyPassword%5D

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@karismann @Zomzog @andrewemery @4brunu @yutaka0m @stefankoppier @e5l

I did not run generators because it fails:

[pool-1-thread-14] Generation failed for csharp: (IllegalArgumentException) The input (net10.0) contains Invalid .NET framework version: net10.0. List of supported versions: netstandard1.3, netstandard1.4, netstandard1.5, netstandard1.6, netstandard2.0, netstandard2.1, net47, net48, net8.0, net9.0
java.lang.IllegalArgumentException: The input (net10.0) contains Invalid .NET framework version: net10.0. List of supported versions: netstandard1.3, netstandard1.4, netstandard1.5, netstandard1.6, netstandard2.0, netstandard2.1, net47, net48, net8.0, net9.0
        at org.openapitools.codegen.languages.CSharpClientCodegen.processOpts(CSharpClientCodegen.java:818)

---

Summary by cubic

Adds Kotlin integration tests to verify query parameter encoding in the Spring RestClient and catch the regression from #22512 where values were wrapped as lists. Tests cover PetApi findByStatus (comma-separated list) and UserApi login (single values).

• Dependencies
  • Add spring-boot-test for MockServerRestClientCustomizer.

^{Written for commit 6767688. Summary will update automatically on new commits.}

[cubic-dev-ai]

No issues found across 3 files

[wing328]

thanks for the PR

i think we will need to update the build.gradle mustache template as well to include this testImlementation.

[pkubowicz]

Yes, I was afraid I was editing in a wrong place, but I could not find a better place for integration tests. I wanted to demonstrate the regression quickly.

I think integration tests (checking what URLs are hit, with what request body string) are very important. With Spring Mock Server, it's easy to write such tests with very little code, and they are also very fast (no port is opened, all happens inside JVM). I would be happy if the integration test suite grows somewhere in the future.

I don't know if integration tests should be part of samples (there are many sample projects, making finding and modifying all integration tests relevant to a feature harder). If you show me a 'cleaner' way to plug in my tests, I am happy to modify my PR.