Independent management max-in-memory-size property

Enhancement

Related: https://github.com/spring-projects/spring-boot/issues/9560
Implemented out of Spring Boot: https://github.com/ilozano2/sc-management-codec-max-size

Motivation

By default, the maximum size of any request payload a Spring boot application can read is 262144 bytes.

This value can be changed using the Spring property spring.codec.max-in-memory-size.
However, increasing the value of this property could expose the production controllers to some risks like DDOS attacks.

Spring Actuator endpoints or the port they listen are not usually exposed to the outside, so it could be safe to increase this value only for the Management Server in a controlled network.

Solution

As implemented in this project I've created, the developer can configure different max-in-memory-size for the management server (aka Spring Actuator endpoints).

management:
  codec:
    max-in-memory-size: 1MB

It is also possible to configure different sizes for management and server.

# Management Server Codec configurations
management:
  codec:
    max-in-memory-size: 1MB

# (original) Server Codec configurations
spring:
  codec:
    max-in-memory-size: 1KB

Start by reading the related Spring Boot issue #9560 and the linked sc-management-codec-max-size implementation. Compare the proposed management.codec.max-in-memory-size and spring.codec.max-in-memory-size settings, then verify that management and application server payload limits can be configured independently without weakening the default server limit.