Jackson Converter for Retrofit in Kotlin

Hello awesome community.

I ended up here after looking all over the places (here & others) about something that is supposed to be simple. More precisely, I am replacing GSON library with Jackson for some reasons.

Basically, what bugs me the most, is that my Jackson Converter seems to be ignored by Retrofit or something.

What I tried :

private val retrofit: Retrofit by lazy {
    Retrofit.Builder()
        .addConverterFactory(
            JacksonConverterFactory.create(jackson)
        )
        .baseUrl(BASE_URL)
        .client(httpClient)
        .build()
}

where jackson is also part of this ApiClient that I am writing

private val jackson: ObjectMapper by lazy {
    ObjectMapper()
        .registerModule(jacksonKotlinModule)
        .setDateFormat(
            SimpleDateFormat(
                "yyyy-MM-dd",
                Locale.getDefault()
            )
        )
}

and, of course jacksonKotlinModule

private val jacksonKotlinModule: KotlinModule by lazy {
    KotlinModule.Builder()
        .configure(KotlinFeature.StrictNullChecks, true)
        .build()
}

All of this in my attempt to get an error when Kotlin non-null fields of a POJO receives a null value from the response of an end-point.

On top of this, I tried the way found in every tutorials about Jackson & Kotlin which is just using jacksonObjectMapper() method available in com.fasterxml.jackson.module.kotlin

Why am I saying that seems to be ignored is because 2 reasons, neither I get any errors or warning or even crashes when I get null response for a non-null Object, neither any Date field isn't formatted as per the DateFormatter that I provided.

It does feel like I might have missed something along the way.. What could I do this in other ways? Oh, I've also tried @JsonFormat(pattern = "yyyy-MM-dd") on a specific field, without success

Later edit: Looks like after more investigations, retrofit does not completely ignore the date format I am providing, but it adapts it somehow. For example "date":"2022-08-24T13:23:10Z" and with SimpleDateFormat("yyyy-MM-dd") it parses the date for year, month, day but also adds 00 for others.. Output is: Wed Aug 24 00:00:00 GTM+03:00 2022