A HEAD to a Container does not return the correct Content-Type

When I do a HEAD request to a Container, I get a Content-Type of application/octet-stream:

$ curl --head https://vincent-test.inrupt.net/public/    
# ...
Content-Type: application/octet-stream; charset=utf-8

even though an actual GET request will return text/turtle:

$ curl --include --request GET https://vincent-test.inrupt.net/public/
# ...
Content-Type: text/turtle

To compare, doing a HEAD to a regular Resource does give me text/turtle:

$ curl --head https://vincent-test.inrupt.net/public/poddit.ttl
# ...
Content-Type: text/turtle; charset=utf-8

$ curl --include --request GET https://vincent-test.inrupt.net/public/poddit.ttl 
# ...
Content-Type: text/turtle

首先复现 issue 中所示的 HEAD 和 GET 请求，然后跟踪服务器如何处理容器与普通资源，以及如何分配 Content-Type。完成的标准是：针对容器的 HEAD 请求与 GET 一致地返回 text/turtle，同时普通资源的行为保持不变。