Check Content-Length on PUT and POST

[namedgraph]

Introduce a aplc:MaxPostSize config parameter and check the Content-Length header of PUT and POST request; reject the request with 413 Request Entity Too Large if it is over the size limit.

[namedgraph]

We can probably leverage Tomcat's maxPostSize by creating a $MAX_POST_SIZE entrypoint param for it, without needing to touch Java code.

[namedgraph]

Looks like Tomcat's maxPostSize doesn't do what I thought it does: https://www.mail-archive.com/search?l=users@tomcat.apache.org&q=subject:%22How+to+upload+Files+larger+than+2GB%22&o=newest&f=1

We need to implement our own subclass of InputStream then, in order to be able to count bytes. It should probably be integrated deep into Core's ModelProvider where the request stream is read.

Checking Content-Length in a ReaderInterceptor sounds much easier, and although the header value can be spoofed, we could use this as an interim solution.

[namedgraph]

Now with tests POST-content-length-413.sh and POST-transfer-chunked-413.sh

[namedgraph]

The implementation could now be simplified by moving it to nginx and configuring using client_max_body_size.

[namedgraph]

Lets keep a check both in nginx and in LinkedDataHub.