feat: pass access_token to coder_git_auth resource (#6713)

This allows template authors to leverage git auth to perform
custom actions, like clone repositories.

testutil/oauth2.go

@@ -0,0 +1,51 @@
+package testutil
+
+import (
+	"context"
+	"net/url"
+	"time"
+
+	"golang.org/x/oauth2"
+)
+
+type OAuth2Config struct {
+	Token           *oauth2.Token
+	TokenSourceFunc OAuth2TokenSource
+}
+
+func (*OAuth2Config) AuthCodeURL(state string, _ ...oauth2.AuthCodeOption) string {
+	return "/?state=" + url.QueryEscape(state)
+}
+
+func (c *OAuth2Config) Exchange(_ context.Context, _ string, _ ...oauth2.AuthCodeOption) (*oauth2.Token, error) {
+	if c.Token == nil {
+		return &oauth2.Token{
+			AccessToken:  "access_token",
+			RefreshToken: "refresh_token",
+			Expiry:       time.Now().Add(time.Hour),
+		}, nil
+	}
+	return c.Token, nil
+}
+
+func (c *OAuth2Config) TokenSource(_ context.Context, _ *oauth2.Token) oauth2.TokenSource {
+	if c.TokenSourceFunc == nil {
+		return OAuth2TokenSource(func() (*oauth2.Token, error) {
+			if c.Token == nil {
+				return &oauth2.Token{
+					AccessToken:  "access_token",
+					RefreshToken: "refresh_token",
+					Expiry:       time.Now().Add(time.Hour),
+				}, nil
+			}
+			return c.Token, nil
+		})
+	}
+	return c.TokenSourceFunc
+}
+
+type OAuth2TokenSource func() (*oauth2.Token, error)
+
+func (o OAuth2TokenSource) Token() (*oauth2.Token, error) {
+	return o()
+}