Add plugin interface code in protobufs package (#921)

Signed-off-by: Shivam Sandbhor <shivam.sandbhor@gmail.com>

pkg/protobufs/plugin_interface.go

@@ -0,0 +1,47 @@
+package protobufs
+
+import (
+	"context"
+
+	plugin "github.com/hashicorp/go-plugin"
+	"google.golang.org/grpc"
+)
+
+type Notifier interface {
+	Notify(ctx context.Context, notification *Notification) (*Empty, error)
+	Configure(ctx context.Context, config *Config) (*Empty, error)
+}
+
+// This is the implementation of plugin.NotifierPlugin so we can serve/consume this.
+type NotifierPlugin struct {
+	// GRPCPlugin must still implement the Plugin interface
+	plugin.Plugin
+	// Concrete implementation, written in Go. This is only used for plugins
+	// that are written in Go.
+	Impl Notifier
+}
+
+type GRPCClient struct{ client NotifierClient }
+
+func (m *GRPCClient) Notify(ctx context.Context, notification *Notification) (*Empty, error) {
+	_, err := m.client.Notify(context.Background(), notification)
+	return &Empty{}, err
+}
+
+func (m *GRPCClient) Configure(ctx context.Context, config *Config) (*Empty, error) {
+	_, err := m.client.Configure(context.Background(), config)
+	return &Empty{}, err
+}
+
+type GRPCServer struct {
+	Impl Notifier
+}
+
+func (p *NotifierPlugin) GRPCServer(broker *plugin.GRPCBroker, s *grpc.Server) error {
+	RegisterNotifierServer(s, p.Impl)
+	return nil
+}
+
+func (p *NotifierPlugin) GRPCClient(ctx context.Context, broker *plugin.GRPCBroker, c *grpc.ClientConn) (interface{}, error) {
+	return &GRPCClient{client: NewNotifierClient(c)}, nil
+}