Update Kotlin version

[nicolas-raoul]

In gradle/libs.versions.toml change:

kotlin = "1.9.22"

to

kotlin = "2.1.0"

... then fix any build error.

---

Gemini also says to do the following, I am not sure how important it is:

1. While you're in the [versions] section, you must also update your Compose BOM (Bill of Materials) to a version that's compatible with the new compiler.

   [versions]
   kotlin = "2.1.0"
   
   # Find your composeBom version and update it.
   # A version like 2024.05.00 or newer is needed.
   # Let's try a recent stable one (e.g., from January 2025):
   androidxComposeBom = "2025.01.00" 

2. In the [plugins] section, you must add the new Compose Compiler plugin, which is now tied to the Kotlin version:

   [plugins]
   # You will see your existing plugins here
   jetbrains-kotlin-android = { id = "org.jetbrains.kotlin.android", version.ref = "kotlin" }
   kotlin-kapt = { id = "org.jetbrains.kotlin.kapt", version.ref = "kotlin" }
   # ...
   
   # Add this line:
   compose-compiler = { id = "org.jetbrains.kotlin.plugin.compose", version.ref = "kotlin" }

In build.gradle.kts:

3. DELETE the old composeOptions block. For Kotlin 2.0 and newer, this is no longer used.

   // DELETE THIS ENTIRE BLOCK:
   composeOptions {
       kotlinCompilerExtensionVersion = "1.5.8"
   }

4. ADD the new plugin to your plugins block at the very top of the file:

   plugins {
       alias(libs.plugins.android.application)
       alias(libs.plugins.jetbrains.kotlin.android)
       alias(libs.plugins.kotlin.kapt)
       alias(libs.plugins.kotlin.parcelize)
       alias(libs.plugins.compose.compiler) // <-- ADD THIS LINE
   }