feat(bluetooth): Proper bond management, identity support for non-splits

* Add `bt` behavior that can be used to perform certain actions,
  such as next/prev identity, reset identity, etc.
  NOTE: Multiple identities is only supported for non-split shields,
  due to missing Zephyr identity functionality for dual
  central/peripheral devices.
* Proper bond reset tied to action, that honors peripheral bonds,
  so folks can reset and pair to other hosts, without breaking
  bonds between splt halves.

app/src/behaviors/behavior_bt.c

@@ -0,0 +1,62 @@
+/*
+ * Copyright (c) 2020 Peter Johanson <peter@peterjohanson.com>
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#define DT_DRV_COMPAT zmk_behavior_bluetooth
+
+#include <device.h>
+#include <drivers/behavior.h>
+
+#include <dt-bindings/zmk/bt.h>
+
+#include <bluetooth/conn.h>
+
+#include <logging/log.h>
+LOG_MODULE_DECLARE(zmk, CONFIG_ZMK_LOG_LEVEL);
+
+#include <zmk/ble.h>
+
+static int on_keymap_binding_pressed(struct device *dev, u32_t position, u32_t command, u32_t arg)
+{
+    switch (command)
+    {
+    case BT_RST_CMD:
+        return zmk_ble_unpair_all();
+    case BT_IDENT_CLR_CMD:
+        return zmk_ble_identity_clear();
+#if CONFIG_BT_ID_MAX != 1
+    case BT_IDENT_NEXT_CMD:
+        return zmk_ble_identity_next();
+    case BT_IDENT_PREV_CMD:
+        return zmk_ble_identity_prev();
+    case BT_IDENT_SEL_CMD:
+        return zmk_ble_identity_select(arg);
+#endif /* BT_ID_MAX != 1 */
+    }
+
+    return -ENOTSUP;
+}
+
+static int behavior_bt_init(struct device *dev)
+{
+    return 0;
+};
+
+static int on_keymap_binding_released(struct device *dev, u32_t position, u32_t command, u32_t arg)
+{
+    return 0;
+}
+
+static const struct behavior_driver_api behavior_bt_driver_api = {
+    .binding_pressed = on_keymap_binding_pressed,
+    .binding_released = on_keymap_binding_released,
+};
+
+DEVICE_AND_API_INIT(behavior_bt, DT_INST_LABEL(0),
+                    behavior_bt_init,
+                    NULL,
+                    NULL,
+                    APPLICATION, CONFIG_KERNEL_INIT_PRIORITY_DEFAULT,
+                    &behavior_bt_driver_api);