Add a model for external apps

Stores their name, website, and credentials

plume-models/src/schema.rs

@@ -1,3 +1,15 @@
+table! {
+    apps (id) {
+        id -> Int4,
+        name -> Text,
+        client_id -> Text,
+        client_secret -> Text,
+        redirect_uri -> Nullable<Text>,
+        website -> Nullable<Text>,
+        creation_date -> Timestamp,
+    }
+}
+
 table! {
     blog_authors (id) {
         id -> Int4,
@@ -192,6 +204,7 @@ joinable!(tags -> posts (post_id));
 joinable!(users -> instances (instance_id));
 
 allow_tables_to_appear_in_same_query!(
+    apps,
     blog_authors,
     blogs,
     comments,