Collection Permissions (#829)

see https://github.com/outline/outline/issues/668

server/models/CollectionUser.js

@@ -0,0 +1,34 @@
+// @flow
+import { DataTypes, sequelize } from '../sequelize';
+
+const CollectionUser = sequelize.define(
+  'collection_user',
+  {
+    permission: {
+      type: DataTypes.STRING,
+      validate: {
+        isIn: [['read', 'read_write']],
+      },
+    },
+  },
+  {
+    timestamps: true,
+  }
+);
+
+CollectionUser.associate = models => {
+  CollectionUser.belongsTo(models.Collection, {
+    as: 'collection',
+    foreignKey: 'collectionId',
+  });
+  CollectionUser.belongsTo(models.User, {
+    as: 'user',
+    foreignKey: 'userId',
+  });
+  CollectionUser.belongsTo(models.User, {
+    as: 'createdBy',
+    foreignKey: 'createdById',
+  });
+};
+
+export default CollectionUser;