Add set up instructions

README.md

@@ -15,3 +15,76 @@ hash - a md5 digest of the ts parameter, your private key and your public key (e
 For example, a user with a public key of "1234" and a private key of "abcd" could construct a valid call as follows: http://gateway.marvel.com/v1/public/comics?ts=1&apikey=1234&hash=ffd275c5130566a2916217b101f26150 (the hash value is the md5 digest of 1abcd1234)
 ```
 
+## Adding the custom modifier in KrakenD
+
+To add the custom modifier to KrakenD it's only needed to create a file like this one in the root of the [KrakenD-CE](https://github.com/devopsfaith/krakend-ce) repository:
+
+*marvel.go:*
+```
+package main
+
+import _ "github.com/taik0/marvelapi-martian_querystring"
+```
+and just follow the regular build steps (`make prepare` and `make`).
+
+To configure KrakenD I needed to add an `extra_config` using the krakend-martian `Namespace` and the custom configuration for the modifier.
+Check also the `whitelist` and `mapping` sections where I set a filter of some fields.
+
+#### KrakenD configuration example
+```
+"endpoints": [
+    {
+        "backend": [
+            {
+                "extra_config": {
+                    "github.com/devopsfaith/krakend-martian": {
+                        "fifo.Group": {
+                            "aggregateErrors": true,
+                            "modifiers": [
+                                {
+                                    "querystring.MarvelModifier": {
+                                        "private": "private_api_key",
+                                        "public": "public_api_key",
+                                        "scope": [
+                                            "request"
+                                        ]
+                                    }
+                                }
+                            ],
+                            "scope": [
+                                "request",
+                                "response"
+                            ]
+                        }
+                    }
+                },
+                "host": [
+                    "http://gateway.marvel.com"
+                ],
+                "url_pattern": "/v1/public/characters?name={name}",
+                "whitelist": [
+                  "data.results",
+                  "attributionHTML"
+                ],
+                "mapping": { "data": "characters"}
+            }
+        ],
+        "endpoint": "/character/{name}",
+        "method": "GET"
+    }
+  ],
+  "extra_config": {
+      "github_com/devopsfaith/krakend-gologging": {
+          "level": "INFO",
+          "prefix": "[KRAKEND]",
+          "stdout": true,
+          "syslog": false
+      }
+  },
+  "name": "My lovely gateway",
+  "port": 8080,
+  "timeout": "3s",
+  "version": 2
+```
+
+