Issue Description

引入nacos后，导致服务启动失败
异常信息： Could not resolve placeholder 'project.version' in value "${project.version}"

Describe what happened (or what feature you want)

异常栈：

2020-08-05 15:47:11.844 [ERROR] [main] [org.springframework.boot.SpringApplication] @@@traceId=@@@ Application startup failed
org.springframework.beans.factory.UnsatisfiedDependencyException: Erro

https://aomediacodec.github.io/av1-avif/#avif-mime-definition

.avif image/avif
.avifs image/avif-sequence

This is being prototyped in Chrome: https://bugs.chromium.org/p/chromium/issues/detail?id=960620

Hi,
thank you for the library. It really improved the way I approach configuration files.
Finally I have types and proper sections.
What I am missing is schema: I would love to be able to enforce that some parameters are obligatory, their type and provide a description, also raise an exception if there is some unknown parameter is configured.
I think I could use something like marshmallow

Similar to the Email validator.