Add CallsAccountProviderInterface

This interface should by implemented by providers for which the user can add
or remove accounts.

src/calls-account-provider.h

@@ -0,0 +1,58 @@
+/*
+ * Copyright (C) 2021 Purism SPC
+ *
+ * This file is part of Calls.
+ *
+ * Calls is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Calls is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Calls.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Author: Evangelos Ribeiro Tzaras <evangelos.tzaras@puri.sm>
+ *
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ *
+ */
+
+#pragma once
+
+#include "calls-account.h"
+#include "calls-credentials.h"
+#include "calls-provider.h"
+
+#include <glib-object.h>
+
+G_BEGIN_DECLS
+
+#define CALLS_TYPE_ACCOUNT_PROVIDER (calls_account_provider_get_type ())
+
+G_DECLARE_INTERFACE (CallsAccountProvider, calls_account_provider, CALLS, ACCOUNT_PROVIDER, CallsProvider);
+
+struct _CallsAccountProviderInterface
+{
+  GTypeInterface parent_iface;
+
+  gboolean           (*add_account)                           (CallsAccountProvider *self,
+                                                               CallsCredentials     *credentials);
+  gboolean           (*remove_account)                        (CallsAccountProvider *self,
+                                                               CallsCredentials     *credentials);
+  CallsAccount      *(*get_account)                           (CallsAccountProvider *self,
+                                                               CallsCredentials     *credentials);
+};
+
+gboolean               calls_account_provider_add_account     (CallsAccountProvider *self,
+                                                               CallsCredentials     *credentials);
+gboolean               calls_account_provider_remove_account  (CallsAccountProvider *self,
+                                                               CallsCredentials     *credentials);
+CallsAccount          *calls_account_provider_get_account     (CallsAccountProvider *self,
+                                                               CallsCredentials     *credentials);
+
+G_END_DECLS