add a tool to check the status of a TUF server (#8428)

Motivation: I often find myself digging through the XML in https://tuf.fleetctl.com to see if/when/what packages have been published in the different release channels, this tool aims to make the process less painful.

```
~/fleet $ go run tools/tuf/status/status.go --help
This is a CLI utility to fetch and filter the entries posted by a TUF repository.
  -key-filter string
    	filter keys using a regular expression (default "stable")
  -url string
    	URL of the TUF repository (default "https://tuf.fleetctl.com")
```

### Examples

- To filter all items on the edge channel use `--key-filter="edge"`
- To filter all items on version `1.3` including patches that run on Linux use `--key-filter="linux/1.3.*"`
- To filter Fleet Desktop items on `1.3.*`, `stable` and `edge` that run on macOS use `--key-filter="desktop/*.*/macos/(1.3.*|stable|edge)"`

### Example output

```
~/fleet $ go run tools/tuf/status/status.go --key-filter="desktop/*.*/macos/(1.3.*|stable|edge)"

Results filtered by "desktop/*.*/macos/(1.3.*|stable|edge)" and sorted by version, platform and key.

VERSION	PLATFORM	KEY                                            	LAST MODIFIED           	SIZE   	ETAG
1.3    	macos   	targets/desktop/macos/1.3/desktop.app.tar.gz   	2022-10-20T00:42:58.000Z	28.4 MB	"ceb7a975880db6ab9aea7907915406e3-4"	
1.3.0  	macos   	targets/desktop/macos/1.3.0/desktop.app.tar.gz 	2022-10-20T00:42:58.000Z	28.4 MB	"ceb7a975880db6ab9aea7907915406e3-4"	
1.3.1  	macos   	targets/desktop/macos/1.3.1/desktop.app.tar.gz 	2022-10-21T20:28:24.000Z	28.5 MB	"3c6641a0df00009f3f076bd6b4fbc748-4"	
edge   	macos   	targets/desktop/macos/edge/desktop.app.tar.gz  	2022-10-21T20:28:37.000Z	28.5 MB	"3c6641a0df00009f3f076bd6b4fbc748-4"	
stable 	macos   	targets/desktop/macos/stable/desktop.app.tar.gz	2022-10-20T00:43:06.000Z	28.4 MB	"ceb7a975880db6ab9aea7907915406e3-4"	
```

tools/tuf/status/README.md

@@ -0,0 +1,19 @@
+# TUF status
+
+```
+~/fleet $ go run tools/tuf/status/status.go --help
+
+This is a CLI utility to fetch and filter the entries posted by a TUF repository.
+
+  -key-filter string
+    	filter keys using a regular expression (default "stable")
+  -url string
+    	URL of the TUF repository (default "https://tuf.fleetctl.com")
+
+
+Examples
+
+- To filter all items on the edge channel use --key-filter="edge"
+- To filter all items on version 1.3 including patches that run on Linux use --key-filter="linux/1.3.*"
+- To filter Fleet Desktop items on 1.3.*, stable and edge that run on macOS use --key-filter="desktop/*.*/macos/(1.3.*|stable|edge)"
+```

tools/tuf/status/status.go

@@ -0,0 +1,139 @@
+package main
+
+import (
+	"encoding/xml"
+	"flag"
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+	"regexp"
+	"sort"
+	"strings"
+
+	"github.com/olekukonko/tablewriter"
+)
+
+type listBucketResult struct {
+	XMLName     xml.Name  `xml:"ListBucketResult"`
+	Text        string    `xml:",chardata"`
+	Xmlns       string    `xml:"xmlns,attr"`
+	Name        string    `xml:"Name"`
+	Prefix      string    `xml:"Prefix"`
+	Marker      string    `xml:"Marker"`
+	MaxKeys     string    `xml:"MaxKeys"`
+	IsTruncated string    `xml:"IsTruncated"`
+	Contents    []content `xml:"Contents"`
+}
+
+type content struct {
+	Text         string `xml:",chardata"`
+	Key          string `xml:"Key"`
+	LastModified string `xml:"LastModified"`
+	ETag         string `xml:"ETag"`
+	Size         int64  `xml:"Size"`
+	StorageClass string `xml:"StorageClass"`
+}
+
+func main() {
+	flag.CommandLine.Usage = func() {
+		fmt.Fprintf(flag.CommandLine.Output(), `
+This is a CLI utility to fetch and filter the entries posted by a TUF repository.
+
+`)
+		flag.CommandLine.PrintDefaults()
+		fmt.Fprintf(flag.CommandLine.Output(), `
+
+Examples
+
+- To filter all items on the edge channel use --key-filter="edge"
+- To filter all items on version 1.3 including patches that run on Linux use --key-filter="linux/1.3.*"
+- To filter Fleet Desktop items on 1.3.*, stable and edge that run on macOS use --key-filter="desktop/*.*/macos/(1.3.*|stable|edge)"
+
+`)
+	}
+	filter := flag.String("key-filter", "stable", "filter keys using a regular expression")
+	url := flag.String("url", "https://tuf.fleetctl.com", "URL of the TUF repository")
+	flag.Parse()
+
+	res, err := http.Get(*url)
+	if err != nil {
+		panic(err)
+	}
+
+	body, err := io.ReadAll(res.Body)
+	if err != nil {
+		panic(err)
+	}
+	defer res.Body.Close()
+
+	var list listBucketResult
+	if err := xml.Unmarshal(body, &list); err != nil {
+		panic(err)
+	}
+
+	if err := printTable(list.Contents, *filter); err != nil {
+		panic(err)
+	}
+}
+
+func printTable(contents []content, filter string) error {
+	data := [][]string{}
+	regFilter, err := regexp.Compile(filter)
+	if err != nil {
+		return err
+	}
+
+	for _, content := range contents {
+		if regFilter.MatchString(content.Key) {
+			r := strings.Split(content.Key, "/")
+			platform, version := r[2], r[3]
+			data = append(data, []string{version, platform, content.Key, content.LastModified, byteCountSI(content.Size), content.ETag})
+		}
+	}
+
+	// sort by version, platform, key
+	sort.Slice(data, func(i, j int) bool {
+		if data[i][0] != data[j][0] {
+			return data[i][0] < data[j][0]
+		}
+
+		if data[i][1] != data[j][1] {
+			return data[i][1] < data[j][1]
+		}
+
+		return data[i][2] < data[j][2]
+	})
+
+	fmt.Printf("\nResults filtered by \"%s\" and sorted by version, platform and key.\n\n", filter)
+	table := tablewriter.NewWriter(os.Stdout)
+	table.SetHeader([]string{"version", "platform", "key", "last modified", "size", "etag"})
+	table.SetAutoWrapText(false)
+	table.SetAutoFormatHeaders(true)
+	table.SetHeaderAlignment(tablewriter.ALIGN_LEFT)
+	table.SetAlignment(tablewriter.ALIGN_LEFT)
+	table.SetCenterSeparator("")
+	table.SetColumnSeparator("")
+	table.SetRowSeparator("")
+	table.SetHeaderLine(false)
+	table.SetBorder(false)
+	table.SetTablePadding("\t")
+	table.SetNoWhiteSpace(true)
+	table.AppendBulk(data)
+	table.Render()
+	return nil
+}
+
+func byteCountSI(b int64) string {
+	const unit = 1000
+	if b < unit {
+		return fmt.Sprintf("%d B", b)
+	}
+	div, exp := int64(unit), 0
+	for n := b / unit; n >= unit; n /= unit {
+		div *= unit
+		exp++
+	}
+	return fmt.Sprintf("%.1f %cB",
+		float64(b)/float64(div), "kMGTPE"[exp])
+}