Throw an exception for suspending factory methods

Suspending factory methods are not supported, and can
have side effects, so it is better to fail explicitly
for such use case.

Closes gh-32719

spring-beans/src/testFixtures/kotlin/org/springframework/beans/testfixture/beans/KotlinConfiguration.kt

@@ -0,0 +1,28 @@
+/*
+ * Copyright 2002-2024 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.beans.testfixture.beans
+
+class KotlinConfiguration {
+
+	fun stringBean(): String {
+		return "Hello"
+	}
+
+	suspend fun suspendingStringBean(): String {
+		return "Hello"
+	}
+}

spring-beans/src/testFixtures/kotlin/org/springframework/beans/testfixture/beans/factory/generator/factory/KotlinFactory.kt

@@ -0,0 +1,29 @@
+/*
+ * Copyright 2002-2024 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.beans.testfixture.beans.factory.generator.factory
+
+class KotlinFactory {
+
+	companion object {
+
+		@JvmStatic
+		fun create() = "test"
+
+		@JvmStatic
+		suspend fun suspendingCreate() = "test"
+	}
+}