Implement OAuth2 server, link oauth:Client and auth::Oauth2Client, implement permission checks

app/models/auth/Group.model.js

@@ -0,0 +1,35 @@
+const { Model } = require('flitter-orm')
+
+// For organizational purposes only.
+class GroupModel extends Model {
+    static get services() {
+        return [...super.services, 'models']
+    }
+
+    static get schema() {
+        return {
+            name: String,
+            user_ids: [String],
+            active: { type: Boolean, default: true },
+        }
+    }
+
+    identifier() {
+        return this.name.toLowerCase().replace(/\s/g, '_')
+    }
+
+    async users() {
+        const User = this.models.get('auth:User')
+        return await User.find({ _id: { $in: this.user_ids.map(x => this.constructor.to_object_id(x)) } })
+    }
+
+    async to_api() {
+        return {
+            id: this.id,
+            name: this.name,
+            user_ids: this.user_ids,
+        }
+    }
+}
+
+module.exports = exports = GroupModel