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/internal/escape/replacer.go

@@ -0,0 +1,8 @@
+package escape
+
+import "github.com/JohannesKaufmann/html-to-markdown/v2/marker"
+
+var placeholderRune rune = marker.MarkerEscaping
+
+// IMPORTANT: Only internally we assume it is only byte
+var placeholderByte byte = marker.BytesMarkerEscaping[0]