Upgrade to Kotlin 1.5.0.

Closes #1438.

parent/pom.xml

@@ -112,7 +112,7 @@
 		<!-- Deprecated: Use junit-vintage-engine and JUnit 4 is included as transitive dependency -->
 		<junit>4.13.2</junit>
 		<junit5>5.7.1</junit5>
-		<kotlin>1.4.32</kotlin>
+		<kotlin>1.5.0</kotlin>
 		<kotlin-coroutines>1.4.3</kotlin-coroutines>
 		<logback>1.2.3</logback>
 		<lombok>1.18.20</lombok>
@@ -1124,6 +1124,9 @@
 					<apiVersion>1.3</apiVersion>
 					<languageVersion>1.3</languageVersion>
 					<skip>${maven.kotlin.skip}</skip>
+					<args>
+						<arg>-Xsuppress-version-warnings</arg>
+					</args>
 				</configuration>
 				<executions>
 					<execution>
@@ -1146,6 +1149,8 @@
 							<goal>test-compile</goal>
 						</goals>
 						<configuration>
+							<apiVersion>1.5</apiVersion>
+							<languageVersion>1.5</languageVersion>
 							<sourceDirs>
 								<sourceDir>${project.basedir}/src/test/kotlin</sourceDir>
 								<sourceDir>${project.basedir}/src/test/java</sourceDir>