Switch to official Vultr API library (#529)

* vultr: Switched to official API library (closes #528)

* vultr: Renamed vultr.VultrApi to vultr.Provider

* vendor: Updated govultr

vendor/github.com/vultr/govultr/os.go

@@ -0,0 +1,84 @@
+package govultr
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"strconv"
+)
+
+// OSService is the interface to interact with the operating system endpoint on the Vultr API
+// Link: https://www.vultr.com/api/#os
+type OSService interface {
+	List(ctx context.Context) ([]OS, error)
+}
+
+// OSServiceHandler handles interaction with the operating system methods for the Vultr API
+type OSServiceHandler struct {
+	client *Client
+}
+
+// OS represents a Vultr operating system
+type OS struct {
+	OsID    int    `json:"OSID"`
+	Name    string `json:"name"`
+	Arch    string `json:"arch"`
+	Family  string `json:"family"`
+	Windows bool   `json:"windows"`
+}
+
+// UnmarshalJSON implements json.Unmarshaller on OS to handle the inconsistent types returned from the Vultr API.
+func (o *OS) UnmarshalJSON(data []byte) (err error) {
+	if o == nil {
+		*o = OS{}
+	}
+
+	var v map[string]interface{}
+	if err := json.Unmarshal(data, &v); err != nil {
+		return err
+	}
+
+	i, err := strconv.Atoi(fmt.Sprintf("%v", v["OSID"]))
+	if err != nil {
+		return err
+	}
+	o.OsID = i
+
+	value := fmt.Sprintf("%v", v["windows"])
+	o.Windows = false
+	if value == "true" {
+		o.Windows = true
+	}
+
+	o.Name = fmt.Sprintf("%v", v["name"])
+	o.Arch = fmt.Sprintf("%v", v["arch"])
+	o.Family = fmt.Sprintf("%v", v["family"])
+
+	return nil
+}
+
+// List retrieves a list of available operating systems.
+// If the Windows flag is true, a Windows license will be included with the instance, which will increase the cost.
+func (o *OSServiceHandler) List(ctx context.Context) ([]OS, error) {
+	uri := "/v1/os/list"
+	req, err := o.client.NewRequest(ctx, http.MethodGet, uri, nil)
+
+	if err != nil {
+		return nil, err
+	}
+
+	osMap := make(map[string]OS)
+
+	err = o.client.DoWithContext(ctx, req, &osMap)
+	if err != nil {
+		return nil, err
+	}
+
+	var oses []OS
+	for _, os := range osMap {
+		oses = append(oses, os)
+	}
+
+	return oses, nil
+}