Polish

Add documentation for server.session.cookie keys

See gh-3240

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

@@ -77,13 +77,13 @@ content into your application; rather pick only the properties that you need.
 	server.display-name= # the display name of the application
 	server.session.timeout= # session timeout in seconds
 	server.session.tracking-modes= # tracking modes (one or more of "cookie" ,"url", "ssl")
-	server.session.cookie.name=
-	server.session.cookie.domain=
-	server.session.cookie.path=
-	server.session.cookie.comment=
-	server.session.cookie.http-only=
-	server.session.cookie.secure=
-	server.session.cookie.max-age=
+	server.session.cookie.name= # session cookie name
+	server.session.cookie.domain= # domain for the session cookie
+	server.session.cookie.path= # path of the session cookie
+	server.session.cookie.comment= # comment for the session cookie
+	server.session.cookie.http-only= # "HttpOnly" flag for the session cookie
+	server.session.cookie.secure= # "Secure" flag for the session cookie
+	server.session.cookie.max-age= # maximum age of the session cookie in seconds
 	server.ssl.enabled=true # if SSL support is enabled
 	server.ssl.client-auth= # want or need
 	server.ssl.key-alias=