Initial merge of faas-containerd

This patch completes part of the work in #20 by porting the code
for faas-containerd in-tree. When tested, I was able to deploy
and then remove figlet from the store on `x86_64`.

In a follow-up PR, duplication will be removed where possible
and consolidated with updated documentation.

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <alexellis2@gmail.com>

pkg/provider/handlers/delete.go

@@ -0,0 +1,68 @@
+package handlers
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"log"
+	"net/http"
+
+	"github.com/alexellis/faasd/pkg/service"
+	"github.com/containerd/containerd"
+	"github.com/containerd/containerd/namespaces"
+	gocni "github.com/containerd/go-cni"
+	"github.com/openfaas/faas/gateway/requests"
+)
+
+func MakeDeleteHandler(client *containerd.Client, cni gocni.CNI) func(w http.ResponseWriter, r *http.Request) {
+
+	return func(w http.ResponseWriter, r *http.Request) {
+
+		if r.Body == nil {
+			http.Error(w, "expected a body", http.StatusBadRequest)
+			return
+		}
+
+		defer r.Body.Close()
+
+		body, _ := ioutil.ReadAll(r.Body)
+		log.Printf("[Delete] request: %s\n", string(body))
+
+		req := requests.DeleteFunctionRequest{}
+		err := json.Unmarshal(body, &req)
+		if err != nil {
+			log.Printf("[Delete] error parsing input: %s\n", err)
+			http.Error(w, err.Error(), http.StatusBadRequest)
+
+			return
+		}
+
+		name := req.FunctionName
+
+		function, err := GetFunction(client, name)
+		if err != nil {
+			msg := fmt.Sprintf("service %s not found", name)
+			log.Printf("[Delete] %s\n", msg)
+			http.Error(w, msg, http.StatusNotFound)
+			return
+		}
+
+		ctx := namespaces.WithNamespace(context.Background(), FunctionNamespace)
+		if function.replicas != 0 {
+			err = DeleteCNINetwork(ctx, cni, client, name)
+			if err != nil {
+				log.Printf("[Delete] error removing CNI network for %s, %s\n", name, err)
+			}
+		}
+
+		containerErr := service.Remove(ctx, client, name)
+		if containerErr != nil {
+			log.Printf("[Delete] error removing %s, %s\n", name, containerErr)
+			http.Error(w, containerErr.Error(), http.StatusInternalServerError)
+			return
+		}
+
+		log.Printf("[Delete] deleted %s\n", name)
+	}
+}