Initialize module and dependencies

vendor/github.com/emersion/go-imap/v2/internal/sasl.go

@@ -0,0 +1,23 @@
+package internal
+
+import (
+	"encoding/base64"
+)
+
+func EncodeSASL(b []byte) string {
+	if len(b) == 0 {
+		return "="
+	} else {
+		return base64.StdEncoding.EncodeToString(b)
+	}
+}
+
+func DecodeSASL(s string) ([]byte, error) {
+	if s == "=" {
+		// go-sasl treats nil as no challenge/response, so return a non-nil
+		// empty byte slice
+		return []byte{}, nil
+	} else {
+		return base64.StdEncoding.DecodeString(s)
+	}
+}