fix: [SDK-4192] downgrade Kotlin from 2.2.0 to 1.9.25

[fadi-george]

Description

One Line Summary

Downgrade Kotlin from 2.2.0 to 1.9.25 to maximize compatibility with consuming projects (including wrapper SDKs on Kotlin 1.9.x).

Details

Motivation

The otel crash reporting PR (#2511) bumped Kotlin from 1.9.25 to 2.2.0. This forces all consumers of the SDK to use Kotlin 2.x, which is a messy change for wrapper SDKs (Flutter, React Native, Cordova, Capacitor, Unity, .NET) and any app still on Kotlin 1.9.x. Since no Kotlin 2.x language features are used in the SDK source code, downgrading to 1.9.25 restores the widest compatibility window — consumers on both 1.9.x and 2.x can use the SDK.

Scope

• SDK build files: kotlinVersion reverted to 1.9.25 in OneSignalSDK/build.gradle
• Otel module: Added -Xskip-metadata-version-check compiler flag to handle transitive dependencies (okio via OkHttp via OpenTelemetry OTLP exporter) compiled with Kotlin 2.x metadata. This is a compile-time-only metadata check skip; binary compatibility is maintained.
• Test fix: OtelIntegrationTest.kt required an explicit !! non-null assertion that Kotlin 2.x's improved smart casts had made unnecessary.
• Demo app: Replaced the Kotlin 2.0+ org.jetbrains.kotlin.plugin.compose plugin with the pre-2.0 composeOptions approach using Compose compiler extension 1.5.15 (the version compatible with Kotlin 1.9.25). Also renamed user-facing "Activity" labels to "Screen".
• No source code changes in the SDK itself — only build config and one test fix.

Testing

Unit testing

• assembleRelease builds successfully (all modules including otel)
• :OneSignal:otel:testReleaseUnitTest passes
• :OneSignal:core:testReleaseUnitTest passes (2 pre-existing SDKInitTests failures unrelated to this change — also fail on main)

Manual testing

Build verified locally via ./gradlew assembleRelease — all 358 tasks succeeded.

Check crash still logs:

Affected code checklist

• Notifications
• Outcomes
• Sessions
• In-App Messaging
• REST API requests
• Public API changes

Checklist

Overview

• I have filled out all REQUIRED sections above
• PR does one thing
• Any Public API changes are explained in the PR details and conform to existing APIs

Testing

• I have included test coverage for these changes, or explained why they are not needed
• All automated tests pass, or I explained why that is not possible
• I have personally tested this on my device, or explained why that is not possible

Final pass

• Code is as readable as possible.
• I have reviewed this PR myself, ensuring it meets each checklist item

Made with Cursor

[abdulraqeeb33]

can we avoid the !! instead add .?

[fadi-george]

Updated to use lateinit var