Refactor repo contents API and add "contents-ext" API (#34822)

See the updated swagger document for details.

modules/structs/repo_file.go

@@ -119,6 +119,11 @@ type FileLinksResponse struct {
 	HTMLURL *string `json:"html"`
 }
 
+type ContentsExtResponse struct {
+	FileContents *ContentsResponse   `json:"file_contents,omitempty"`
+	DirContents  []*ContentsResponse `json:"dir_contents,omitempty"`
+}
+
 // ContentsResponse contains information about a repo's entry's (dir, file, symlink, submodule) metadata and content
 type ContentsResponse struct {
 	Name          string `json:"name"`
@@ -145,6 +150,9 @@ type ContentsResponse struct {
 	// `submodule_git_url` is populated when `type` is `submodule`, otherwise null
 	SubmoduleGitURL *string            `json:"submodule_git_url"`
 	Links           *FileLinksResponse `json:"_links"`
+
+	LfsOid  *string `json:"lfs_oid"`
+	LfsSize *int64  `json:"lfs_size"`
 }
 
 // FileCommitResponse contains information generated from a Git commit for a repo's file.