Bluetooth: CAP: Commander discovery support

Implement the CAP Commander discovery function.

Adds support for it in the shell.

This includes initial babblesim and unit testing as well.

Signed-off-by: Emil Gydesen <emil.gydesen@nordicsemi.no>

subsys/bluetooth/audio/shell/cap_commander.c

@@ -0,0 +1,79 @@
+/**
+ * @file
+ * @brief Shell APIs for Bluetooth CAP commander
+ *
+ * Copyright (c) 2023 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+#include <stdlib.h>
+
+#include <zephyr/types.h>
+#include <zephyr/shell/shell.h>
+#include <zephyr/bluetooth/conn.h>
+#include <zephyr/bluetooth/audio/cap.h>
+
+#include "shell/bt.h"
+#include "audio.h"
+
+static void cap_discover_cb(struct bt_conn *conn, int err,
+			    const struct bt_csip_set_coordinator_csis_inst *csis_inst)
+{
+	if (err != 0) {
+		shell_error(ctx_shell, "discover failed (%d)", err);
+		return;
+	}
+
+	shell_print(ctx_shell, "discovery completed%s", csis_inst == NULL ? "" : " with CSIS");
+}
+
+static struct bt_cap_commander_cb cbs = {
+	.discovery_complete = cap_discover_cb,
+};
+
+static int cmd_cap_commander_discover(const struct shell *sh, size_t argc, char *argv[])
+{
+	static bool cbs_registered;
+	int err;
+
+	if (default_conn == NULL) {
+		shell_error(sh, "Not connected");
+		return -ENOEXEC;
+	}
+
+	if (ctx_shell == NULL) {
+		ctx_shell = sh;
+	}
+
+	if (!cbs_registered) {
+		bt_cap_commander_register_cb(&cbs);
+		cbs_registered = true;
+	}
+
+	err = bt_cap_commander_discover(default_conn);
+	if (err != 0) {
+		shell_error(sh, "Fail: %d", err);
+	}
+
+	return err;
+}
+
+static int cmd_cap_commander(const struct shell *sh, size_t argc, char **argv)
+{
+	if (argc > 1) {
+		shell_error(sh, "%s unknown parameter: %s", argv[0], argv[1]);
+	} else {
+		shell_error(sh, "%s Missing subcommand", argv[0]);
+	}
+
+	return -ENOEXEC;
+}
+
+SHELL_STATIC_SUBCMD_SET_CREATE(
+	cap_commander_cmds,
+	SHELL_CMD_ARG(discover, NULL, "Discover CAS", cmd_cap_commander_discover, 1, 0),
+	SHELL_SUBCMD_SET_END
+);
+
+SHELL_CMD_ARG_REGISTER(cap_commander, &cap_commander_cmds, "Bluetooth CAP commander shell commands",
+		       cmd_cap_commander, 1, 1);