Add a model for external apps

Stores their name, website, and credentials

plume-models/src/apps.rs

@@ -0,0 +1,18 @@
+use chrono::NaiveDateTime;
+
+use schema::apps;
+
+pub struct App {
+    pub id: i32,
+    pub name: String,
+    pub client_id: String,
+    pub client_secret: String,
+    pub redirect_uri: Option<String>,
+    pub website: Option<String>,    
+    pub creation_date: NaiveDateTime,
+}
+
+impl App {
+    get!(apps, App);
+    insert!(apps, NewApp);
+}