p1: /v2/scrape, /v1/fetch, auth, CLI, contract tests

Single Fetcher.Fetch on the Guard that holds DenyPrefixes. skipTlsVerification
is ignored. No 502. keys add writes the secret only to --out. Release binary
has no -test-allow-prefix.

vendor/github.com/JohannesKaufmann/dom/attr.go

@@ -0,0 +1,68 @@
+package dom
+
+import (
+	"bytes"
+	"strings"
+
+	"golang.org/x/net/html"
+)
+
+func GetAttribute(node *html.Node, key string) (string, bool) {
+	for _, attr := range node.Attr {
+		if attr.Key == key {
+			return attr.Val, true
+		}
+	}
+	return "", false
+}
+func GetAttributeOr(node *html.Node, key string, fallback string) string {
+	for _, attr := range node.Attr {
+		if attr.Key == key {
+			return attr.Val
+		}
+	}
+	return fallback
+}
+
+func GetClasses(node *html.Node) []string {
+	val, found := GetAttribute(node, "class")
+	if !found {
+		return nil
+	}
+
+	return strings.Fields(val)
+}
+
+func HasID(node *html.Node, expectedID string) bool {
+	val, found := GetAttribute(node, "id")
+	if !found {
+		return false
+	}
+	return strings.TrimSpace(val) == expectedID
+}
+func HasClass(node *html.Node, expectedClass string) bool {
+	classes := GetClasses(node)
+	for _, class := range classes {
+		if class == expectedClass {
+			return true
+		}
+	}
+	return false
+}
+
+// - - - - //
+
+func collectText(n *html.Node, buf *bytes.Buffer) {
+	if n.Type == html.TextNode {
+		buf.WriteString(n.Data)
+	}
+	for c := n.FirstChild; c != nil; c = c.NextSibling {
+		collectText(c, buf)
+	}
+}
+
+func CollectText(node *html.Node) string {
+	var buf bytes.Buffer
+	collectText(node, &buf)
+	return buf.String()
+}