Defines a message handler. Permissions can be passed via opts param to validate request's rights. Event handler receives parsed and validated payload.

Options

- `:unauthorized_handler` - function to be called when user is not authorized to perform the action.
- `:invalid_params_handler` - function to be called when params are invalid.
- `:permissions` - list of permissions to check.

Examples

1. As a function definition:
```
message event_name(payload, socket) do
  # Code
end
```
2. As a function declaration:
```
message(
  :event_name,
  payload_template,
  opts
)

def event_name(payload, socket) do
  # Code
end
```

This way you can create event handler by yourself thus allowing you to make use of multiple function pattern matching.

A shorter version of the full-fat message macro. The difference is that this helper manages to execute your code in a separate process, prepares ctx and then automatically sends given response with the metadata and request_id set up. Data and metadata are also mapped to the serializable versions (using map_response).

No longer shall we forget do these extra steps a-ha :).

Extra variables available

• ctx - just the result of user_ctx(socket) call (should contain %UserContext{} struct with information about current user)
• channel_pid - this is the PID of the channel (in case you want to send custom message to this channel)

Defines a payload schema for first following message handler (that consumes the schema and prevents further use of this schema). Payload schema is a map with keys and types. For schema documentation see Tarams library.

Creates a handle_info definition which simplifies the syntax required for this code. From this:

def handle_info({:event, param1, param2, ...}, socket) do
  ...code
  {:noreply, socket}
end

To this:

sub event(param1, param2, ..., socket) do
  ...code
  {:noreply, socket}
end