Add structs holding metadata for the books

src/book/metadata.rs

@@ -0,0 +1,71 @@
+#[derive(Debug, Clone)]
+pub struct BookMetadata {
+    pub title: String,
+    pub description: String,
+
+    pub language: Language,
+
+    authors: Vec<Author>,
+    translators: Vec<Author>,
+}
+
+#[derive(Debug, Clone)]
+pub struct Author {
+    name: String,
+    email: Option<String>,
+}
+
+#[derive(Debug, Clone)]
+pub struct Language {
+    name: String,
+    code: String,
+}
+
+
+impl BookMetadata {
+    pub fn new(title: &str) -> Self {
+        BookMetadata {
+            title: title.to_owned(),
+            description: String::new(),
+
+            language: Language::default(),
+
+            authors: Vec::new(),
+            translators: Vec::new(),
+        }
+    }
+
+    pub fn set_description(&mut self, description: &str) -> &mut Self {
+        self.description = description.to_owned();
+        self
+    }
+
+    pub fn add_author(&mut self, author: Author) -> &mut Self {
+        self.authors.push(author);
+        self
+    }
+}
+
+impl Author {
+    pub fn new(name: &str) -> Self {
+        Author {
+            name: name.to_owned(),
+            email: None,
+        }
+    }
+
+    pub fn with_email(mut self, email: &str) -> Self {
+        self.email = Some(email.to_owned());
+        self
+    }
+}
+
+
+impl Default for Language {
+    fn default() -> Self {
+        Language {
+            name: String::from("English"),
+            code: String::from("en"),
+        }
+    }
+}