feat(capabilities): capabilities topic

- Adds the `capabilities` endpoint for the device

Signed-off-by: Luca Zaninotto <[email protected]>

lib/astarte_vmq_plugin.ex

@@ -151,6 +151,9 @@ defmodule Astarte.VMQ.Plugin do
           control_path = "/" <> Enum.join(control_path_tokens, "/")
           publish_control_message(realm, device_id, control_path, payload, timestamp)
 
+        [^realm, ^device_id, "capabilities"] ->
+          publish_capabilities(realm, device_id, payload, timestamp)
+
         [^realm, ^device_id, interface | path_tokens] ->
           path = "/" <> Enum.join(path_tokens, "/")
           publish_data(realm, device_id, interface, path, payload, timestamp)
@@ -207,6 +210,10 @@ defmodule Astarte.VMQ.Plugin do
     publish(realm, device_id, payload, "data", timestamp, additional_headers)
   end
 
+  defp publish_capabilities(realm, device_id, payload, timestamp) do
+    publish(realm, device_id, payload, "capabilities", timestamp)
+  end
+
   defp publish_control_message(realm, device_id, control_path, payload, timestamp) do
     additional_headers = [x_astarte_control_path: control_path]
 

test/astarte_vmq_plugin_test.exs

@@ -422,6 +422,32 @@ defmodule Astarte.VMQ.PluginTest do
     assert String.starts_with?(message_id, message_id_prefix(@realm, @device_id, timestamp))
   end
 
+  test "device capabilities on_publish" do
+    payload = "payload"
+    capabilities_topic = [@realm, @device_id, "capabilities"]
+
+    Plugin.on_publish(
+      :dontcare,
+      {:dontcare, @device_base_path},
+      :dontcare,
+      capabilities_topic,
+      payload,
+      :dontcare
+    )
+
+    assert_receive {:amqp_msg, ^payload, %{headers: headers, timestamp: timestamp} = _metadata}
+
+    # 5 seconds
+    assert_in_delta timestamp, now_us_x10_timestamp(), 50_000_000
+
+    assert %{
+             "x_astarte_vmqamqp_proto_ver" => 1,
+             "x_astarte_msg_type" => "capabilities",
+             "x_astarte_realm" => @realm,
+             "x_astarte_device_id" => @device_id
+           } = amqp_headers_to_map(headers)
+  end
+
   test "device data on_publish" do
     path = "/some/data/path"
     interface = "com.my.Interface"