feat: Update Kotlin SDK to use Gson instead of Jackson

[mistryrakesh]

This PR updates the kotlin SDK to use Gson instead of Jackson for deserialization (We were already using gson to serialize).

This fixes:

• Jackson serialization bug Jackson renames primitive boolean field by removing 'is' resulting in much clean and concise code.
• In some cases prevents breaking of the SDK due to API changes by ignoring unknown fields (How to decode JSON with unknown field using Gson?). e.g. When SDK is generated from an older instance but has to access a newer instance.

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Fixes #825 🦕

[github-actions]

Codegen Tests

  1 files    6 suites   59s ⏱️
58 tests 46 ✔️ 12 💤 0 ❌

Results for commit e31ccff.

[jkaster]

Great update. Nice to have cleaner and more flexible code.

bin/smoke kotlin

passes.

Can you add a test that verifies the graceful handling of unknown fields?

[github-actions]

Codegen Tests

  1 files  ±0    6 suites  ±0   59s ⏱️ +9s
58 tests ±0  46 ✔️ ±0  12 💤 ±0  0 ❌ ±0 

Results for commit 870ab75. ± Comparison against base commit 283cbd5.

[mistryrakesh]

Hey @jkaster thanks for reviewing!

I have added a smoke test (SmokeTest.testIgnoreUnknownFields()) which basically fetches all users and deserializes it into DummyUser object. The DummyUser class is a subset of the User class. When the server sends a response User object the Gson deserializer ignores extra properties and creates the DummyUser object.

Using the Jackson deserializer the test fails with error:

java.lang.Error: GET /users com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "avatar_url" (class DummyUser), not marked as ignorable (4 known properties: "display_name", "id", "credentials_api3", "email"])
 at [Source: (StringReader); line: 1, column: 1260] (through reference chain: java.lang.Object[][0]->DummyUser["avatar_url"]).message
java.lang.AssertionError: java.lang.Error: GET /users com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "avatar_url" (class DummyUser), not marked as ignorable (4 known properties: "display_name", "id", "credentials_api3", "email"])
 at [Source: (StringReader); line: 1, column: 1260] (through reference chain: java.lang.Object[][0]->DummyUser["avatar_url"]).message
	at org.junit.Assert.fail(Assert.java:88)
	at kotlin.test.junit.JUnitAsserter.fail(JUnitSupport.kt:56)
	at kotlin.test.Asserter$DefaultImpls.assertTrue(Assertions.kt:226)
	at kotlin.test.junit.JUnitAsserter.assertTrue(JUnitSupport.kt:30)
	at kotlin.test.Asserter$DefaultImpls.assertTrue(Assertions.kt:236)
	at kotlin.test.junit.JUnitAsserter.assertTrue(JUnitSupport.kt:30)
	at kotlin.test.AssertionsKt__AssertionsKt.assertTrue(Assertions.kt:40)
	at kotlin.test.AssertionsKt.assertTrue(Unknown Source)
	at TestSmoke.testIgnoreUnknownFields(TestSmoke.kt:212)

[jkaster]

@mistryrakesh This is great stuff! I really appreciate your contributions here.

[jkaster]

Nicely done! It's great to have better resilience for the Kotlin SDK.