[medusa-interfaces] : Adds decorator functionality to BaseService (#39)

Plugins and projects can add decorators in services. E.g. if a plugin needs to load some additional information on carts the plugin can register a decorator via: `cartService.addDecorator(someFunc)` which will be available later through `cartService.runDecorators()`.

packages/medusa-plugin-permissions/package.json

@@ -1,35 +0,0 @@
-{
-  "name": "medusa-plugin-permissions",
-  "version": "1.0.0",
-  "description": "Role permission for Medusa core",
-  "main": "dist/index.js",
-  "repository": {
-    "type": "git",
-    "url": "https://github.com/medusajs/medusa",
-    "directory": "packages/medusa-plugin-permissions"
-  },
-  "scripts": {
-    "build": "babel src --out-dir dist/ --ignore **/__tests__",
-    "prepare": "cross-env NODE_ENV=production npm run build",
-    "watch": "babel -w src --out-dir dist/ --ignore **/__tests__",
-    "test": "jest"
-  },
-  "author": "Oliver Juhl",
-  "license": "AGPL-3.0-or-later",
-  "devDependencies": {
-    "@babel/cli": "^7.7.5",
-    "@babel/core": "^7.7.5",
-    "@babel/plugin-proposal-class-properties": "^7.7.4",
-    "@babel/plugin-transform-runtime": "^7.7.6",
-    "@babel/preset-env": "^7.7.5",
-    "@babel/runtime": "^7.7.6",
-    "cross-env": "^5.2.1",
-    "jest": "^24.9.0"
-  },
-  "dependencies": {
-    "mongoose": "^5.8.0",
-    "medusa-test-utils": "^1.0.0",
-    "medusa-core-utils": "^1.0.0",
-    "medusa-interfaces": "^1.0.0"
-  }
-}