Move plugin context events into separate plugin

Signed-off-by: Derek McGowan <derek@mcg.dev>

plugin/context.go

@@ -34,7 +34,9 @@ type InitContext struct {
 	Config       interface{}
 	Address      string
 	TTRPCAddress string
-	Events       *exchange.Exchange
+
+	// deprecated: will be removed in 2.0, use plugin.EventType
+	Events *exchange.Exchange
 
 	Meta *Meta // plugins can fill in metadata at init.
 
@@ -135,6 +137,19 @@ func (i *InitContext) GetAll() []*Plugin {
 	return i.plugins.ordered
 }
 
+// GetByID returns the plugin of the given type and ID
+func (i *InitContext) GetByID(t Type, id string) (interface{}, error) {
+	ps, err := i.GetByType(t)
+	if err != nil {
+		return nil, err
+	}
+	p, ok := ps[id]
+	if !ok {
+		return nil, errors.Wrapf(errdefs.ErrNotFound, "no %s plugins with id %s", t, id)
+	}
+	return p.Instance()
+}
+
 // GetByType returns all plugins with the specific type.
 func (i *InitContext) GetByType(t Type) (map[string]*Plugin, error) {
 	p, ok := i.plugins.byTypeAndID[t]