Introduce CallsSecretStore to store credentials

src/meson.build

@@ -38,6 +38,7 @@ calls_deps = [ dependency('gobject-2.0', version: '>= 2.58'),
                dependency('libebook-contacts-1.2'),
                dependency('folks'),
                dependency('libcallaudio-0.1'),
+               dependency('libsecret-1'),
              ]
 
 calls_vala_deps = [
@@ -111,6 +112,7 @@ calls_sources = files(['calls-message-source.c', 'calls-message-source.h',
                        'calls-account-overview.c', 'calls-account-overview.h',
                        'calls-account-row.c', 'calls-account-row.h',
                        'calls-settings.c', 'calls-settings.h',
+                       'calls-secret-store.c', 'calls-secret-store.h',
                       ]) + calls_generated_sources
 
 calls_config_data = config_data