http map not fully supported

[chrisnovakovic]

Describe the bug

This is similar to #101 but slightly different because of the extra expressiveness of map compared to types.

The analyser doesn't take into account the special syntax of http map blocks, in which directives are one of a handful of special directives or arbitrary strings. The analyser also doesn't support any of the special directives listed in the ngx_http_map_module documentation. This means that crossplane doesn't recognise Nginx configurations containing map blocks as valid when running in strict mode, which verifies that directive names are present in the analyser's allowlist. A similar problem occurs when check_ctx=True is set via the API.

To Reproduce

Run crossplane parse --strict on the following Nginx configuration:

http {
    map $http_host $name {
        hostnames;
        volatile;
        default 0;
        example.com 1;
        include map_values.conf;
    }
}

# map_values.conf:

*.example.com 2;
\volatile 3;

This outputs:

{"status":"failed","errors":[{"file":"nginx.conf","error":"unknown directive \"hostnames\" in nginx.conf:3","line":3},{"file":"nginx.conf","error":"unknown directive \"volatile\" in nginx.conf:4","line":4},{"file":"nginx.conf","error":"unknown directive \"default\" in nginx.conf:5","line":5},{"file":"nginx.conf","error":"unknown directive \"example.com\" in nginx.conf:6","line":6},{"file":"map_values.conf","error":"unknown directive \"*.example.com\" in map_values.conf:1","line":1},{"file":"map_values.conf","error":"unknown directive \"\\volatile\" in map_values.conf:2","line":2}],"config":[{"file":"nginx.conf","status":"failed","errors":[{"error":"unknown directive \"hostnames\" in nginx.conf:3","line":3},{"error":"unknown directive \"volatile\" in nginx.conf:4","line":4},{"error":"unknown directive \"default\" in nginx.conf:5","line":5},{"error":"unknown directive \"example.com\" in nginx.conf:6","line":6}],"parsed":[{"directive":"http","line":1,"args":[],"block":[{"directive":"map","line":2,"args":["$http_host","$name"],"block":[{"directive":"include","line":7,"args":["map_values.conf"],"includes":[1]}]}]}]},{"file":"map_values.conf","status":"failed","errors":[{"error":"unknown directive \"*.example.com\" in map_values.conf:1","line":1},{"error":"unknown directive \"\\volatile\" in map_values.conf:2","line":2}],"parsed":[]}]}

Expected behavior

No errors are encountered, and an AST is printed.

Your environment

crossplane v0.5.7 (although the problem also exists on master)