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/error.go

@@ -0,0 +1,91 @@
+package acme
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"net/http"
+	"strings"
+)
+
+const (
+	tosAgreementError = "Terms of service have changed"
+	invalidNonceError = "urn:ietf:params:acme:error:badNonce"
+)
+
+// RemoteError is the base type for all errors specific to the ACME protocol.
+type RemoteError struct {
+	StatusCode int    `json:"status,omitempty"`
+	Type       string `json:"type"`
+	Detail     string `json:"detail"`
+}
+
+func (e RemoteError) Error() string {
+	return fmt.Sprintf("acme: Error %d - %s - %s", e.StatusCode, e.Type, e.Detail)
+}
+
+// TOSError represents the error which is returned if the user needs to
+// accept the TOS.
+// TODO: include the new TOS url if we can somehow obtain it.
+type TOSError struct {
+	RemoteError
+}
+
+// NonceError represents the error which is returned if the
+// nonce sent by the client was not accepted by the server.
+type NonceError struct {
+	RemoteError
+}
+
+type domainError struct {
+	Domain string
+	Error  error
+}
+
+// ObtainError is returned when there are specific errors available
+// per domain. For example in ObtainCertificate
+type ObtainError map[string]error
+
+func (e ObtainError) Error() string {
+	buffer := bytes.NewBufferString("acme: Error -> One or more domains had a problem:\n")
+	for dom, err := range e {
+		buffer.WriteString(fmt.Sprintf("[%s] %s\n", dom, err))
+	}
+	return buffer.String()
+}
+
+func handleHTTPError(resp *http.Response) error {
+	var errorDetail RemoteError
+
+	contentType := resp.Header.Get("Content-Type")
+	if contentType == "application/json" || strings.HasPrefix(contentType, "application/problem+json") {
+		err := json.NewDecoder(resp.Body).Decode(&errorDetail)
+		if err != nil {
+			return err
+		}
+	} else {
+		detailBytes, err := ioutil.ReadAll(limitReader(resp.Body, maxBodySize))
+		if err != nil {
+			return err
+		}
+		errorDetail.Detail = string(detailBytes)
+	}
+
+	errorDetail.StatusCode = resp.StatusCode
+
+	// Check for errors we handle specifically
+	if errorDetail.StatusCode == http.StatusForbidden && errorDetail.Detail == tosAgreementError {
+		return TOSError{errorDetail}
+	}
+
+	if errorDetail.StatusCode == http.StatusBadRequest && errorDetail.Type == invalidNonceError {
+		return NonceError{errorDetail}
+	}
+
+	return errorDetail
+}
+
+func handleChallengeError(chlng challenge) error {
+	return chlng.Error
+}