Fix URL related escaping for oauth2 (#37334) (#37340)

Backport #37334 by wxiaoguang

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

routers/web/auth/oauth.go

@@ -36,9 +36,7 @@ import (
 
 // SignInOAuth handles the OAuth2 login buttons
 func SignInOAuth(ctx *context.Context) {
-	// the provider is escaped by backend QueryEscape and frontend urlQueryEscape
-	// so always use QueryUnescape to decode it
-	authName, _ := url.QueryUnescape(ctx.PathParamRaw("provider"))
+	authName := ctx.PathParam("provider")
 	authSource, err := auth.GetActiveOAuth2SourceByAuthName(ctx, authName)
 	if err != nil {
 		ctx.ServerError("SignIn", err)