Update license header and javadoc.

Original Pull Request: #2129

Author: christophstrobl

Diff for: src/main/java/org/springframework/data/redis/core/ReactiveRedisSessionCallback.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2017-2021 the original author or authors.
+ * Copyright 2021 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.
@@ -23,7 +23,7 @@
  * Generic callback interface for code that wants to use the same {@link ReactiveRedisConnection} avoiding connection
  * allocation overhead upon each Template API method call. Allows to execute any number of operations on a single
  * {@link ReactiveRedisConnection}, using any type and number of commands.
- * <p>
+ * <p />
  * This is particularly useful for issuing multiple calls on the same connection.
  *
  * @param <T>
@@ -36,13 +36,13 @@ public interface ReactiveRedisSessionCallback<K, V, T> {
 	/**
 	 * Gets called by {@link ReactiveRedisOperations#executeInSession(ReactiveRedisSessionCallback)} with an active Redis
 	 * connection. Does not need to care about activating or closing the {@link ReactiveRedisConnection}.
-	 * <p>
+	 * <p />
 	 * Allows for returning a result object created within the callback, i.e. a domain object or a collection of domain
 	 * objects.
 	 *
 	 * @param operations template associated with a connection.
-	 * @return a result object publisher
-	 * @throws DataAccessException in case of custom exceptions
+	 * @return a result object {@link Publisher}.
+	 * @throws DataAccessException in case of custom exceptions.
 	 */
 	Publisher<T> doWithOperations(ReactiveRedisOperations<K, V> operations) throws DataAccessException;
 }

Diff for: src/main/java/org/springframework/data/redis/core/ReactiveRedisTemplate.java

@@ -180,6 +180,7 @@ public <T> Flux<T> createFlux(ReactiveRedisCallback<T> callback) {
 	 *
 	 * @param callback must not be {@literal null}
 	 * @return a {@link Flux} wrapping the {@link ReactiveRedisCallback}.
+	 * @since 2.6
 	 */
 	<T> Flux<T> doCreateFlux(ReactiveRedisCallback<T> callback) {
 
@@ -209,6 +210,7 @@ public <T> Mono<T> createMono(ReactiveRedisCallback<T> callback) {
 	 *
 	 * @param callback must not be {@literal null}
 	 * @return a {@link Mono} wrapping the {@link ReactiveRedisCallback}.
+	 * @since 2.6
 	 */
 	<T> Mono<T> doCreateMono(ReactiveRedisCallback<T> callback) {