Add ThreadLocalAccessor for LocaleContext and RequestAttributes

Add `ThreadLocalAccessor` implementations:
- `LocaleThreadLocalAccessor`
- `RequestAttributesThreadLocalAccessor`

See gh-32243

spring-context/src/main/java/org/springframework/context/i18n/LocaleContextThreadLocalAccessor.java

@@ -0,0 +1,55 @@
+/*
+ * 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.context.i18n;
+
+import io.micrometer.context.ThreadLocalAccessor;
+
+/**
+ * Adapt {@link LocaleContextHolder} to the {@link ThreadLocalAccessor} contract to assist
+ * the Micrometer Context Propagation library with {@link LocaleContext} propagation.
+ * @author Tadaya Tsuyukubo
+ * @since 6.2
+ */
+public class LocaleContextThreadLocalAccessor implements ThreadLocalAccessor<LocaleContext> {
+
+	/**
+	 * Key under which this accessor is registered in
+	 * {@link io.micrometer.context.ContextRegistry}.
+	 */
+	public static final String KEY = LocaleContextThreadLocalAccessor.class.getName() + ".KEY";
+
+	@Override
+	public Object key() {
+		return KEY;
+	}
+
+	@Override
+	public LocaleContext getValue() {
+		return LocaleContextHolder.getLocaleContext();
+	}
+
+	@Override
+	public void setValue(LocaleContext value) {
+		LocaleContextHolder.setLocaleContext(value);
+	}
+
+	@Override
+	public void setValue() {
+		LocaleContextHolder.resetLocaleContext();
+	}
+
+}