Add grpc plugin (#2758)

* Add grpc plugin

* remove stale readmes

server/grpc/handler.go

@@ -0,0 +1,66 @@
+package grpc
+
+import (
+	"reflect"
+
+	"go-micro.dev/v5/registry"
+	"go-micro.dev/v5/server"
+)
+
+type rpcHandler struct {
+	name      string
+	handler   interface{}
+	endpoints []*registry.Endpoint
+	opts      server.HandlerOptions
+}
+
+func newRpcHandler(handler interface{}, opts ...server.HandlerOption) server.Handler {
+	options := server.HandlerOptions{
+		Metadata: make(map[string]map[string]string),
+	}
+
+	for _, o := range opts {
+		o(&options)
+	}
+
+	typ := reflect.TypeOf(handler)
+	hdlr := reflect.ValueOf(handler)
+	name := reflect.Indirect(hdlr).Type().Name()
+
+	var endpoints []*registry.Endpoint
+
+	for m := 0; m < typ.NumMethod(); m++ {
+		if e := extractEndpoint(typ.Method(m)); e != nil {
+			e.Name = name + "." + e.Name
+
+			for k, v := range options.Metadata[e.Name] {
+				e.Metadata[k] = v
+			}
+
+			endpoints = append(endpoints, e)
+		}
+	}
+
+	return &rpcHandler{
+		name:      name,
+		handler:   handler,
+		endpoints: endpoints,
+		opts:      options,
+	}
+}
+
+func (r *rpcHandler) Name() string {
+	return r.name
+}
+
+func (r *rpcHandler) Handler() interface{} {
+	return r.handler
+}
+
+func (r *rpcHandler) Endpoints() []*registry.Endpoint {
+	return r.endpoints
+}
+
+func (r *rpcHandler) Options() server.HandlerOptions {
+	return r.opts
+}