GH-3858: Add ImapIdleChASpec.reconnectDelay()

Fixes https://github.com/spring-projects/spring-integration/issues/3858

spring-integration-mail/src/main/java/org/springframework/integration/mail/dsl/ImapIdleChannelAdapterSpec.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2021 the original author or authors.
+ * Copyright 2014-2022 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.
@@ -52,6 +52,7 @@ import org.springframework.util.Assert;
  *
  * @author Gary Russell
  * @author Artem Bilan
+ * @author Freya Nair
  *
  * @since 5.0
  */
@@ -383,6 +384,17 @@ public class ImapIdleChannelAdapterSpec
 		return this;
 	}
 
+	/**
+	 * The time between connection attempts in milliseconds (default 10 seconds).
+	 * @param reconnectDelay the reconnectDelay to set.
+	 * @return the spec.
+	 * @since 6.0
+	 */
+	public ImapIdleChannelAdapterSpec reconnectDelay(long reconnectDelay) {
+		this.target.setReconnectDelay(reconnectDelay);
+		return this;
+	}
+
 	/**
 	 * Determine how the content is rendered.
 	 * @param simpleContent true for simple content.