Fix agent API to accept protobuf content type

The :accepts plug in the agent_api pipeline was only allowing JSON,
which caused 406 errors when the agent sent protobuf requests.

Changes:
- Register application/x-protobuf MIME type in config
- Add protobuf to agent_api pipeline accepts list
- Agent can now successfully communicate using protobuf format

config/config.exs

@@ -22,6 +22,11 @@ config :logger, :default_formatter,
   format: "$time $metadata[$level] $message\n",
   metadata: [:request_id]
 
+# Register protobuf MIME type for agent API
+config :mime, :types, %{
+  "application/x-protobuf" => ["protobuf"]
+}
+
 # Filter sensitive parameters from logs
 config :phoenix, :filter_parameters, ["password", "snmp_community", "secret", "token", "api_key"]
 

lib/towerops_web/router.ex

@@ -19,7 +19,7 @@ defmodule ToweropsWeb.Router do
   end
 
   pipeline :agent_api do
-    plug :accepts, ["json"]
+    plug :accepts, ["json", "protobuf"]
     plug ToweropsWeb.Plugs.AgentAuth
   end