Add versioned persistent configuration protocol

adapter_configuration.h

@@ -0,0 +1,21 @@
+#pragma once
+
+#include <stddef.h>
+#include <stdint.h>
+
+constexpr uint16_t ADAPTER_CONFIGURATION_SCHEMA_VERSION = 1;
+constexpr size_t ADAPTER_CONFIGURATION_ENCODED_SIZE = 4;
+constexpr uint16_t ADAPTER_PAIRING_WINDOW_SECONDS_MIN = 10;
+constexpr uint16_t ADAPTER_PAIRING_WINDOW_SECONDS_MAX = 300;
+constexpr uint16_t ADAPTER_PAIRING_WINDOW_SECONDS_DEFAULT = 60;
+
+struct AdapterConfiguration {
+    uint16_t pairing_window_seconds =
+        ADAPTER_PAIRING_WINDOW_SECONDS_DEFAULT;
+};
+
+AdapterConfiguration adapter_configuration_default();
+bool adapter_configuration_encode(const AdapterConfiguration& configuration,
+                                  uint8_t* output, size_t output_size);
+bool adapter_configuration_decode(const uint8_t* payload, size_t payload_size,
+                                  AdapterConfiguration* output);