Clarify how to configure a Filter's order

Closes gh-18266

Author: wilkinsona

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

@@ -2676,7 +2676,10 @@ Here are a few examples of Filters and their respective order (lower order value
 
 It is usually safe to leave Filter beans unordered.
 
-If a specific order is required, you should avoid configuring a Filter that reads the request body at `Ordered.HIGHEST_PRECEDENCE`, since it might go against the character encoding configuration of your application.
+If a specific order is required, you should annotate the `Filter` with `@Order` or make it implement `Ordered`.
+You cannot configure the order of a `Filter` by annotating its bean method with `@Order`.
+If you cannot change the `Filter` class to add `@Order` or implement `Ordered`, you must define a `FilterRegistrationBean` for the `Filter` and set the registration bean's order using the `setOrder(int)` method.
+Avoid configuring a Filter that reads the request body at `Ordered.HIGHEST_PRECEDENCE`, since it might go against the character encoding configuration of your application.
 If a Servlet filter wraps the request, it should be configured with an order that is less than or equal to `OrderedFilter.REQUEST_WRAPPER_FILTER_MAX_ORDER`.
 
 WARNING: Take care when registering `Filter` beans since they are initialized very early in the application lifectyle.