Second commit

added few test, first api to add book

internal/api/mapper.go

@@ -0,0 +1,9 @@
+package api
+
+import "git.artlef.fr/PersonalLibraryManager/internal/model"
+
+func (b bookPostCreate) toBook() model.Book {
+	return model.Book{Title: b.Title,
+		Author: b.Author,
+		Rating: b.Rating}
+}