Abstraction for Certificate Storage (+ vault storage) (#406)

* new abstraction around storage

* re-work completely to fit new acme package pre-solving paradigm

* vault storage plugin

* add some vendor

* delete old vendor pinning mechanism

vendor/github.com/xenolf/lego/acme/http_challenge.go

@@ -0,0 +1,42 @@
+package acme
+
+import (
+	"fmt"
+
+	"github.com/xenolf/lego/log"
+)
+
+type httpChallenge struct {
+	jws      *jws
+	validate validateFunc
+	provider ChallengeProvider
+}
+
+// HTTP01ChallengePath returns the URL path for the `http-01` challenge
+func HTTP01ChallengePath(token string) string {
+	return "/.well-known/acme-challenge/" + token
+}
+
+func (s *httpChallenge) Solve(chlng challenge, domain string) error {
+
+	log.Infof("[%s] acme: Trying to solve HTTP-01", domain)
+
+	// Generate the Key Authorization for the challenge
+	keyAuth, err := getKeyAuthorization(chlng.Token, s.jws.privKey)
+	if err != nil {
+		return err
+	}
+
+	err = s.provider.Present(domain, chlng.Token, keyAuth)
+	if err != nil {
+		return fmt.Errorf("[%s] error presenting token: %v", domain, err)
+	}
+	defer func() {
+		err := s.provider.CleanUp(domain, chlng.Token, keyAuth)
+		if err != nil {
+			log.Warnf("[%s] error cleaning up: %v", domain, err)
+		}
+	}()
+
+	return s.validate(s.jws, domain, chlng.URL, challenge{Type: chlng.Type, Token: chlng.Token, KeyAuthorization: keyAuth})
+}