Add missing Javadoc

Closes gh-8743

web/src/main/java/org/springframework/security/web/authentication/switchuser/SwitchUserFilter.java

@@ -538,6 +538,14 @@ public class SwitchUserFilter extends GenericFilterBean
 		this.switchUserAuthorityChanger = switchUserAuthorityChanger;
 	}
 
+	/**
+	 * Sets the {@link UserDetailsChecker} that is called on the target user
+	 * whenever the user is switched.
+	 *
+	 * @param userDetailsChecker the {@link UserDetailsChecker} that checks the
+	 * status of the user that is being switched to. Defaults to
+	 * {@link AccountStatusUserDetailsChecker}.
+	 */
 	public void setUserDetailsChecker(UserDetailsChecker userDetailsChecker) {
 		this.userDetailsChecker = userDetailsChecker;
 	}