Decoding of key from file specified by spring.security.oauth2.resourceserver.public-key-location fails on Windows

[wilkinsona]

When the key is written to a file that uses \r\n line separators (as is typically the case on Windows) decoding fails reporting an illegal Base64 character. The root cause looks something like this:

 Caused by: java.lang.IllegalArgumentException: Illegal base64 character d
  at java.util.Base64$Decoder.decode0(Base64.java:714)
  at java.util.Base64$Decoder.decode(Base64.java:526)
  at java.util.Base64$Decoder.decode(Base64.java:549)
  at org.springframework.boot.autoconfigure.security.oauth2.resource.reactive.ReactiveOAuth2ResourceServerJwkConfiguration.getKeySpec(ReactiveOAuth2ResourceServerJwkConfiguration.java:76)
  at org.springframework.boot.autoconfigure.security.oauth2.resource.reactive.ReactiveOAuth2ResourceServerJwkConfiguration.jwtDecoderByPublicKeyValue(ReactiveOAuth2ResourceServerJwkConfiguration.java:69)
  at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
  at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
  at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
  at java.lang.reflect.Method.invoke(Method.java:498)
  at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:154)
  ... 81 more

Switching to a MIME decoder should fix the problem on Windows while not adversely affecting other platforms.