Provide a configuration option to enable lazy initialization

Closes gh-15870

spring-boot-project/spring-boot-docs/src/main/asciidoc/appendix/application-properties.adoc

@@ -125,6 +125,7 @@ content into your application. Rather, pick only the properties that you need.
 	# APPLICATION SETTINGS ({sc-spring-boot}/SpringApplication.{sc-ext}[SpringApplication])
 	spring.main.allow-bean-definition-overriding=false # Whether bean definition overriding, by registering a definition with the same name as an existing definition, is allowed.
 	spring.main.banner-mode=console # Mode used to display the banner when the application runs.
+	spring.main.lazy-initialization=false # Whether initialization should be performed lazily.
 	spring.main.sources= # Sources (class names, package names, or XML resource locations) to include in the ApplicationContext.
 	spring.main.web-application-type= # Flag to explicitly request a specific type of web application. If not set, auto-detected based on the classpath.
 

spring-boot-project/spring-boot-docs/src/main/asciidoc/spring-boot-features.adoc

@@ -91,6 +91,36 @@ the `debug` property as follows:
 
 
 
+[[boot-features-lazy-initialization]]
+=== Lazy Initialization
+`SpringApplication` allows an application to be initialized lazily. When lazy
+initialization is enabled, beans are created as they are needed rather than during
+application startup. As a result, enabling lazy initialization can reduce the time that
+it takes your application to start. In a web application, enabling lazy initialization
+will result in many web-related beans not being initialized until an HTTP request is
+received.
+
+A downside of lazy initialization is that it can delay the discovery of a problem with
+the application. If a misconfigured bean is initialized lazily, a failure will no longer
+occur during startup and the problem will only become apparent when the bean is
+initialized. Care must also be taken to ensure that the JVM has sufficient memory to
+accommodate all of the application's beans and not just those that are initialized during
+startup. For these reasons, lazy initialization is not enabled by default and it is
+recommended that fine-tuning of the JVM's heap size is done before enabling lazy
+initialization.
+
+Lazy initialization can be enabled programatically using the `lazyInitialization` method
+on `SpringApplicationBuilder` or the `setLazyInitialization` method on
+`SpringApplication`. Alternatively, it can be enabled using the
+`spring.main.lazy-initialization` property as shown in the following example:
+
+[source,properties,indent=0]
+----
+	spring.main.lazy-initialization=true
+----
+
+
+
 [[boot-features-banner]]
 === Customizing the Banner
 The banner that is printed on start up can be changed by adding a `banner.txt` file to