Move local device_id into public settings section

Local ID is going to be used by local auth, so no reason to keep it
private.

BUG=25766813

Change-Id: I7cfb190c77246a4445f813f16c8af353284cc7e9
Reviewed-on: https://weave-review.googlesource.com/1797
Reviewed-by: Alex Vakulenko <avakulenko@google.com>

include/weave/settings.h

diff --git a/include/weave/settings.h b/include/weave/settings.h
index e5d21b0..1c8b095 100644
--- a/include/weave/settings.h
+++ b/include/weave/settings.h
@@ -64,6 +64,9 @@
   // Cloud ID of the registered device. Empty if device is not registered.
   std::string cloud_id;
 
+  // Local device id.
+  std::string device_id;
+
   // Internal options to tweak some library functionality. External code should
   // avoid using them.
   bool wifi_auto_setup_enabled{true};

src/config.h

diff --git a/src/config.h b/src/config.h
index fe9e159..bab50ca 100644
--- a/src/config.h
+++ b/src/config.h
@@ -24,7 +24,6 @@
 class Config final {
  public:
   struct Settings : public weave::Settings {
-    std::string device_id;
     std::string refresh_token;
     std::string robot_account;
     std::string last_configured_ssid;