The resource system now tracks both the time when a resource was last
modified and the revision number of the resource. This allows working
Last-Modified and ETag headers to be generated by the REST API.
The If-Modified-Since and If-None-Match request headers are not yet
processed and using them will always return the resource instead of a 304
Not Modified response.
The actual list of headers is not known when the request is first
generated. This prevents the headers from being generated in admin.cc
which handles things on a lower level.
The moving of the header generation is done with the OPTIONS method in
mind. This header needs to be generated inside the RootResource class
which manages the navigation of the resources.
Cleaned up various parts of the resource, request and response class
headers.
Moved `using` declarations into .cc files.
Made the Resource class non-copyable as it isn't really meant to be
copied.
The standard response headers are now generated at a higher level. This
reduces the scope of the HttpResponse class making it a leaner wrapper
around a few simple variables, namely the JSON body of the response.
The HttpRequest now exposes the Host header that the client sent. This
allows resource relations to be real links that work without modification.
The HTTP side of the REST API is better handled with an actual
library. The libmicrohttpd library provides a convenient way of handling
the HTTP traffic between the clients and MaxScale.
The resource handler system is now usable but it doesn't perform anything
useful. Although, this will allows it to be tested for correctness.
Minor fixes to HttpResponse output and renaming of functions.
The class now generates default headers. The ETag and Last-Modified tags
do not represent any actual modification time or resource hash.
The basic functionality of the HTTP responses is tested by the core test
suite. More advanced testing of the whole REST API is still required.
Removed the static `create` functions as only the JSON parsing version
could generated errors and even then the errors were unlikely. By
replacing the static creator function with a normal constructor, the
HttpResponse class can now also be created on the stack making its use
easier.
The HTTP response class simplifies the response creation. The next step is
to add generation of all the default headers that are needed by the REST
API.
