Refactor the utils package to other areas (#538)

* Refactor the utils package to other areas

Move cookieSession functions to cookie session store
& align the double implementation of SecretBytes to be
united and housed under encryption

* Remove unused Provider SessionFromCookie/CookieForSession

These implementations aren't used, these are handled in the cookie store.

* Add changelog entry for session/utils refactor

pkg/encryption/cipher.go

@@ -17,6 +17,29 @@ import (
 	"time"
 )
 
+// SecretBytes attempts to base64 decode the secret, if that fails it treats the secret as binary
+func SecretBytes(secret string) []byte {
+	b, err := base64.URLEncoding.DecodeString(addPadding(secret))
+	if err == nil {
+		return []byte(addPadding(string(b)))
+	}
+	return []byte(secret)
+}
+
+func addPadding(secret string) string {
+	padding := len(secret) % 4
+	switch padding {
+	case 1:
+		return secret + "==="
+	case 2:
+		return secret + "=="
+	case 3:
+		return secret + "="
+	default:
+		return secret
+	}
+}
+
 // cookies are stored in a 3 part (value + timestamp + signature) to enforce that the values are as originally set.
 // additionally, the 'value' is encrypted so it's opaque to the browser