varlink-idl: introduce c/.h file for common varlink IDL structures

Some structures we'll use in various varlink interfaces, move them to a
common .c/.h file. For now this is only the dual timestamp object, but
there will be more soon.

src/shared/meson.build

@@ -177,6 +177,7 @@ shared_sources = files(
         'user-record.c',
         'userdb-dropin.c',
         'userdb.c',
+        'varlink-idl-common.c',
         'varlink-io.systemd.BootControl.c',
         'varlink-io.systemd.Credentials.c',
         'varlink-io.systemd.Hostname.c',

src/shared/varlink-idl-common.c

@@ -0,0 +1,12 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include "sd-varlink-idl.h"
+
+#include "varlink-idl-common.h"
+
+SD_VARLINK_DEFINE_STRUCT_TYPE(
+                Timestamp,
+                SD_VARLINK_FIELD_COMMENT("Timestamp in µs in the CLOCK_REALTIME clock (wallclock)"),
+                SD_VARLINK_DEFINE_FIELD(realtime, SD_VARLINK_INT, SD_VARLINK_NULLABLE),
+                SD_VARLINK_FIELD_COMMENT("Timestamp in µs in the CLOCK_MONOTONIC clock"),
+                SD_VARLINK_DEFINE_FIELD(monotonic, SD_VARLINK_INT, SD_VARLINK_NULLABLE));

src/shared/varlink-idl-common.h

@@ -0,0 +1,6 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+#include "sd-varlink-idl.h"
+
+extern const sd_varlink_symbol vl_type_Timestamp;

src/shared/varlink-io.systemd.Machine.c

@@ -3,6 +3,7 @@
 #include "sd-varlink-idl.h"
 
 #include "bus-polkit.h"
+#include "varlink-idl-common.h"
 #include "varlink-io.systemd.Machine.h"
 
 static SD_VARLINK_DEFINE_METHOD(
@@ -21,13 +22,6 @@ static SD_VARLINK_DEFINE_METHOD(
                 SD_VARLINK_DEFINE_INPUT(allocateUnit,      SD_VARLINK_BOOL,   SD_VARLINK_NULLABLE),
                 VARLINK_DEFINE_POLKIT_INPUT);
 
-static SD_VARLINK_DEFINE_STRUCT_TYPE(
-                Timestamp,
-                SD_VARLINK_FIELD_COMMENT("Timestamp in µs in the CLOCK_REALTIME clock (wallclock)"),
-                SD_VARLINK_DEFINE_FIELD(realtime, SD_VARLINK_INT, SD_VARLINK_NULLABLE),
-                SD_VARLINK_FIELD_COMMENT("Timestamp in µs in the CLOCK_MONOTONIC clock"),
-                SD_VARLINK_DEFINE_FIELD(monotonic, SD_VARLINK_INT, SD_VARLINK_NULLABLE));
-
 static SD_VARLINK_DEFINE_METHOD(
                 Unregister,
                 SD_VARLINK_FIELD_COMMENT("The name of a machine to unregister."),