New Registrar: CSC Global (#827)

* CSC Global Registrar provider

* better error handling. Coding standards.

* Just return the error

providers/cscglobal/cscglobalProvider.go

@@ -0,0 +1,72 @@
+package cscglobal
+
+import (
+	"fmt"
+	"sort"
+	"strings"
+
+	"github.com/StackExchange/dnscontrol/v3/models"
+	"github.com/StackExchange/dnscontrol/v3/providers"
+)
+
+/*
+
+CSC Global Registrar:
+
+Info required in `creds.json`:
+   - api-key             Api Key
+   - user-token          User Token
+   - notification_emails (optional) Comma seperated list of email addresses to send notifications to
+*/
+
+func init() {
+	providers.RegisterRegistrarType("CSCGLOBAL", newCscGlobal)
+}
+
+func newCscGlobal(m map[string]string) (providers.Registrar, error) {
+	api := &api{}
+
+	api.key, api.token = m["api-key"], m["user-token"]
+	if api.key == "" || api.token == "" {
+		return nil, fmt.Errorf("missing CSC Global api-key and/or user-token")
+	}
+
+	if m["notification_emails"] != "" {
+		api.notifyEmails = strings.Split(m["notification_emails"], ",")
+	}
+
+	return api, nil
+}
+
+// GetRegistrarCorrections gathers corrections that would being n to match dc.
+func (c *api) GetRegistrarCorrections(dc *models.DomainConfig) ([]*models.Correction, error) {
+	nss, err := c.getNameservers(dc.Name)
+	if err != nil {
+		return nil, err
+	}
+	foundNameservers := strings.Join(nss, ",")
+
+	expected := []string{}
+	for _, ns := range dc.Nameservers {
+		if ns.Name[len(ns.Name)-1] == '.' {
+			// When this code was written ns.Name never included a single trailing dot.
+			// If that changes, the code should change too.
+			return nil, fmt.Errorf("Name server includes a trailing dot, has the API changed?")
+		}
+		expected = append(expected, ns.Name)
+	}
+	sort.Strings(expected)
+	expectedNameservers := strings.Join(expected, ",")
+
+	if foundNameservers != expectedNameservers {
+		return []*models.Correction{
+			{
+				Msg: fmt.Sprintf("Update nameservers %s -> %s", foundNameservers, expectedNameservers),
+				F: func() error {
+					return c.updateNameservers(expected, dc.Name)
+				},
+			},
+		}, nil
+	}
+	return nil, nil
+}