sign: API changes for public keys and CLI keys format

API changes:
- added function `ostree_sign_add_pk()` for multiple public keys using.
- `ostree_sign_set_pk()` now substitutes all previously added keys.
- added function `ostree_sign_load_pk()` allowed to load keys from file.
- `ostree_sign_ed25519_load_pk()` able to load the raw keys list from file.
- use base64 encoded public and private ed25519 keys for CLI and keys file.

Signed-off-by: Denis Pynkin <denis.pynkin@collabora.com>

src/libostree/ostree-sign.h

@@ -68,8 +68,12 @@ struct _OstreeSignInterface
                        GVariant *public_key,
                        GError **error);
 
+  gboolean (* add_pk) (OstreeSign *self,
+                       GVariant *public_key,
+                       GError **error);
+
   gboolean (* load_pk) (OstreeSign *self,
-                        gchar *remote_name,
+                        GVariant *options,
                         GError **error);
 
 };
@@ -126,9 +130,14 @@ gboolean ostree_sign_set_pk (OstreeSign *self,
                              GVariant *public_key,
                              GError **error);
 
+_OSTREE_PUBLIC
+gboolean ostree_sign_add_pk (OstreeSign *self,
+                             GVariant *public_key,
+                             GError **error);
+
 _OSTREE_PUBLIC
 gboolean ostree_sign_load_pk (OstreeSign *self,
-                              gchar *remote_name,
+                              GVariant *options,
                               GError **error);