Support oauth codes

auth/provider/oauth/oauth.go

@@ -3,7 +3,6 @@ package oauth
 import (
 	"fmt"
 	"net/url"
-	"strings"
 
 	"github.com/micro/go-micro/v2/auth/provider"
 )
@@ -29,17 +28,25 @@ func (o *oauth) Options() provider.Options {
 	return o.opts
 }
 
-func (o *oauth) Endpoint() string {
+func (o *oauth) Endpoint(opts ...provider.EndpointOption) string {
+	var options provider.EndpointOptions
+	for _, o := range opts {
+		o(&options)
+	}
+
 	params := make(url.Values)
 	params.Add("response_type", "code")
 
+	if len(options.Code) > 0 {
+		params.Add("code", options.Code)
+	}
+
 	if clientID := o.opts.ClientID; len(clientID) > 0 {
 		params.Add("client_id", clientID)
 	}
 
 	if scope := o.opts.Scope; len(scope) > 0 {
-		// spaces are url encoded since this cannot be passed in env vars
-		params.Add("scope", strings.ReplaceAll(scope, "%20", " "))
+		params.Add("scope", scope)
 	}
 
 	if redir := o.Redirect(); len(redir) > 0 {