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/html-to-markdown/v2/converter/escape.go

@@ -0,0 +1,89 @@
+package converter
+
+import (
+	"unicode/utf8"
+
+	"github.com/JohannesKaufmann/html-to-markdown/v2/marker"
+)
+
+const (
+	actionKeep   = iota
+	actionEscape = iota
+)
+
+// IMPORTANT: Only internally we assume it is only byte
+var placeholderByte byte = marker.BytesMarkerEscaping[0]
+
+func (conv *Converter) escapeContent(chars []byte) []byte {
+	if conv.escapeMode == EscapeModeDisabled {
+		return chars
+	}
+
+	newChars := make([]byte, 0, len(chars))
+	for index := 0; index < len(chars); index++ {
+		if chars[index] == '\u0000' {
+			// For security reasons, the Unicode character U+0000 must be replaced with the REPLACEMENT CHARACTER (U+FFFD).
+			newChars = append(newChars, []byte(string('\ufffd'))...)
+			continue
+		}
+
+		r, _ := utf8.DecodeRune(chars[index:])
+
+		isMarkdownChar := conv.checkIsEscapedChar(r)
+		if isMarkdownChar {
+			newChars = append(newChars, placeholderByte, chars[index])
+		} else {
+			newChars = append(newChars, chars[index])
+		}
+	}
+
+	return newChars
+}
+
+func (conv *Converter) unEscapeContent(chars []byte) []byte {
+	if conv.escapeMode == EscapeModeDisabled {
+		return chars
+	}
+
+	checkElements := func(index int) int {
+		for _, handler := range conv.getUnEscapeHandlers() {
+			if skip := handler.Value(chars, index); skip != -1 {
+				return skip
+			}
+		}
+
+		return -1
+	}
+
+	changes := make([]uint8, len(chars))
+	for index := 0; index < len(chars); index++ {
+
+		if chars[index] != placeholderByte {
+			continue
+		}
+		if index+1 >= len(chars) {
+			break
+		}
+
+		skip := checkElements(index + 1)
+		if skip == -1 {
+			continue
+		}
+		changes[index] = actionEscape
+		index += skip - 1
+	}
+
+	newChars := make([]byte, 0, len(chars))
+	for index, char := range chars {
+		if char != placeholderByte {
+			newChars = append(newChars, char)
+			continue
+		}
+
+		// What to do with this placeholder? Should we escape or not?
+		if changes[index] == actionEscape {
+			newChars = append(newChars, '\\')
+		}
+	}
+	return newChars
+}