Use TemplateClassResolver.SAFER_RESOLVER by default

[Jacques Le Roux]

Hi,

After reading https://ackcent.com/blog/in-depth-freemarker-template-injection/ I wonder why we have not TemplateClassResolver.SAFER_RESOLVER[1] used 
by default, like there is:

    The api_builtin_enabled configuration setting must be set to true. Its default is false (at least as of 2.3.22) for not lowering the security of 
existing applications.[2]

Is there a reason?

Thanks

Jacques

[1] 
https://freemarker.apache.org/docs/api/freemarker/core/TemplateClassResolver.html#SAFER_RESOLVER
[2] 
https://freemarker.apache.org/docs/ref_builtins_expert.html#ref_buitin_api_and_has_api