Some quickstarts still using a regular client instead of component client in integration tests

[efgpinto]

Found at least 2 quickstarts that still use a regular WebClient in integration tests, inteads of the component client.
I think we should use the ComponentClient unless there is a specific reason to use a WebClient.

Samples in need of update, here and here.

[aludwiko]

Actually, a lot of samples use WebClient in tests, and I have some second thoughts about changing this. For instance, it might be surprising to see the ComponentClient in tests for samples/quickstarts that don't use it in the implementation. Would require some additional cognitive load to understand what it is, search the docs, etc., and we aimed to make them simple to digest. WDYT @ennru ?

[ennru]

I agree, these introductory examples will be easier to consume with less Kalix specifics. So let's keep the Spring WebClient unless the code is in a more advanced Kalix context already.