Upgrade to Kotlin 1.9.0.

Closes #2049

Author: emrearslan

parent/pom.xml

@@ -115,7 +115,7 @@
 		<!-- Deprecated: Use junit-vintage-engine and JUnit 4 is included as transitive dependency -->
 		<junit>4.13.2</junit>
 		<junit5>5.9.3</junit5>
-		<kotlin>1.8.21</kotlin>
+		<kotlin>1.9.0</kotlin>
 		<kotlin-coroutines>1.7.2</kotlin-coroutines>
 		<logback>1.4.1</logback>
 		<micrometer>1.12.0-SNAPSHOT</micrometer>