blogposts: refactor, create newPost func

blogposts/blogposts.go

@@ -33,6 +33,12 @@ func getPost(fileSystem fs.FS, f fs.DirEntry) (Post, error) {
 	}
 	defer postFile.Close()
 
+	return newPost(postFile)
+}
+
+// NOTE: Does newPost have to be coupled to an fs.File ?
+// Do we use all the methods and data from this type? What do we really need?
+func newPost(postFile fs.File) (Post, error) {
 	postData, err := io.ReadAll(postFile)
 	if err != nil {
 		return Post{}, err