Add custom code generation for bean definition property values

This commits allows ValueCodeGenerator$Delegate implementations to be
loaded from `META-INF/spring/aot.factories` and considered for code
generation of bean definition property values. This default behavior
in DefaultBeanRegistrationCodeFragments can be customized as usual.

Closes gh-31427

spring-beans/src/testFixtures/java/org/springframework/beans/testfixture/beans/factory/aot/CustomBean.java

@@ -0,0 +1,36 @@
+/*
+ * Copyright 2002-2023 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.aot;
+
+/**
+ * A bean that uses {@link CustomPropertyValue}.
+ *
+ * @author Stephane Nicoll
+ */
+public class CustomBean {
+
+	private CustomPropertyValue customPropertyValue;
+
+	public CustomPropertyValue getCustomPropertyValue() {
+		return this.customPropertyValue;
+	}
+
+	public void setCustomPropertyValue(CustomPropertyValue customPropertyValue) {
+		this.customPropertyValue = customPropertyValue;
+	}
+
+}

spring-beans/src/testFixtures/java/org/springframework/beans/testfixture/beans/factory/aot/CustomPropertyValue.java

@@ -0,0 +1,40 @@
+/*
+ * Copyright 2002-2023 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.aot;
+
+import org.springframework.aot.generate.ValueCodeGenerator;
+import org.springframework.aot.generate.ValueCodeGenerator.Delegate;
+import org.springframework.javapoet.CodeBlock;
+
+/**
+ * A custom value with its code generator {@link Delegate} implementation.
+ *
+ * @author Stephane Nicoll
+ */
+public record CustomPropertyValue(String value) {
+
+	public static class ValueCodeGeneratorDelegate implements Delegate {
+		@Override
+		public CodeBlock generateCode(ValueCodeGenerator valueCodeGenerator, Object value) {
+			if (value instanceof CustomPropertyValue data) {
+				return CodeBlock.of("new $T($S)", CustomPropertyValue.class, data.value);
+			}
+			return null;
+		}
+	}
+
+}

spring-beans/src/testFixtures/resources/META-INF/spring/aot.factories

@@ -0,0 +1,2 @@
+org.springframework.aot.generate.ValueCodeGenerator$Delegate=\
+org.springframework.beans.testfixture.beans.factory.aot.CustomPropertyValue$ValueCodeGeneratorDelegate