Add ability to broadcast to everyone but yoursefl

[NathanFlurry]

Motivation

Add ability to broadcast to conns except for the conn that sent the RPC request. Only available on ActionContext.

Implementation

actor({
  actions: {
    foo: c => {
      c.broadcast("bar", 123, { excludeSelf: true });
    }
  }
});

excludeSelf naming could use some work.

Alternative Implementations

exclude

Add a more generic option for just excluding connection IDs.

actor({
  actions: {
    foo: c => {
      c.broadcast("bar", 123, { exclude: [c.conn.id] });
    }
  }
});

It might make sense to implement both, since broadcast to all but self is a very common operation.

broadcastToOthers

Same functionality as excludeSelf but a separate method name.

Prior Art

Socket.io:

  io.except(excludedSocketId).emit('broadcastEvent', data);

[linear]

ACTR-136 Add ability to broadcast to everyone but yoursefl

[abcxff]

a note, broadcast has signature broadcast(name, ...args), so we can't fit a options object { excludeSelf: true } at the last param.

One way of going about this is to have two methods, broadcast(name, ...args) and broadcastWith(opts, name, ...args) aka broadcastWithOptions(opts, name, ...args) . where broadcast just wraps around broadcastWith({}, name, …args)

[abcxff]

Completed with #939