add vars tests

Signed-off-by: Mohammed Al Sahaf <msaa1990@gmail.com>

caddytest/spec/http/vars/spec.hurl

@@ -0,0 +1,125 @@
+# Configure Caddy with vars directive
+POST http://localhost:2019/load
+Content-Type: text/caddyfile
+```
+{
+	skip_install_trust
+	http_port     9080
+	https_port    9443
+	local_certs
+}
+localhost {
+	vars my_var "custom_value"
+	vars another_var "another_value"
+	respond "{vars.my_var} {vars.another_var}"
+}
+```
+
+# Variables are accessible in placeholders
+GET https://localhost:9443
+[Options]
+insecure: true
+HTTP 200
+[Asserts]
+body == "custom_value another_value"
+
+
+# Configure Caddy with vars using placeholders
+POST http://localhost:2019/load
+Content-Type: text/caddyfile
+```
+{
+	skip_install_trust
+	http_port     9080
+	https_port    9443
+	local_certs
+}
+localhost {
+	vars request_path {path}
+	vars request_method {method}
+	respond "Path: {vars.request_path}, Method: {vars.request_method}"
+}
+```
+
+# Variables can be set from request placeholders
+GET https://localhost:9443/test/path
+[Options]
+insecure: true
+HTTP 200
+[Asserts]
+body == "Path: /test/path, Method: GET"
+
+
+# POST method is captured correctly
+POST https://localhost:9443/another
+[Options]
+insecure: true
+HTTP 200
+[Asserts]
+body == "Path: /another, Method: POST"
+
+
+# Configure Caddy with vars in route
+POST http://localhost:2019/load
+Content-Type: text/caddyfile
+```
+{
+	skip_install_trust
+	http_port     9080
+	https_port    9443
+	local_certs
+}
+localhost {
+	route /api/* {
+		vars api_version "v1"
+		respond "API {vars.api_version}"
+	}
+	respond "Not API"
+}
+```
+
+# Variables are scoped to their route
+GET https://localhost:9443/api/users
+[Options]
+insecure: true
+HTTP 200
+[Asserts]
+body == "API v1"
+
+
+# Outside the route, variables are not set
+GET https://localhost:9443/other
+[Options]
+insecure: true
+HTTP 200
+[Asserts]
+body == "Not API"
+
+
+# Configure Caddy with vars overwriting
+POST http://localhost:2019/load
+Content-Type: text/caddyfile
+```
+{
+	skip_install_trust
+	http_port     9080
+	https_port    9443
+	local_certs
+}
+localhost {
+	# without `route`, middlewares are sorted an unstable sort
+	route {
+		vars my_var "2"
+		vars my_var "1"
+	}
+	respond "{vars.my_var}"
+}
+```
+
+# Later vars directives overwrite earlier ones
+GET https://localhost:9443
+[Options]
+insecure: true
+HTTP 200
+[Asserts]
+body == "1"