Support oauth codes

auth/provider/basic/basic.go

@@ -25,7 +25,7 @@ func (b *basic) Options() provider.Options {
 	return b.opts
 }
 
-func (b *basic) Endpoint() string {
+func (b *basic) Endpoint(...provider.EndpointOption) string {
 	return ""
 }
 

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 {

auth/provider/provider.go

@@ -12,7 +12,7 @@ type Provider interface {
 	// Options returns the options of a provider
 	Options() Options
 	// Endpoint for the provider
-	Endpoint() string
+	Endpoint(...EndpointOption) string
 	// Redirect url incase of UI
 	Redirect() string
 }
@@ -26,3 +26,15 @@ type Grant struct {
 	// Scopes associated with grant
 	Scopes []string
 }
+
+type EndpointOptions struct {
+	Code string
+}
+
+type EndpointOption func(*EndpointOptions)
+
+func WithCode(c string) EndpointOption {
+	return func(o *EndpointOptions) {
+		o.Code = c
+	}
+}