Feat(medusa): implement feature flags (#1768)

* feat: add feature flag loading in projects

* fix: make feature flag consume itself

* fix: rename container registration to featureFlagRouter

* fix: refactor

* behavioral feature flags

* add environment to server

* limit "useTemplateDb" to non feature flagged migrations

* filter migrations and entities according to those which are enabled in the environment

* run only migrations that are enabled when running 'medusa migrations run'

* add logging to the featureflag loader

* initial implementation of featureFlagEntity

* column descriptors

* initial startServerWithEnv (to be refactored)

* update commands

* final touches

* update loaders to fix unit tests

* enable all batch job tests

* update seed method

* add api test capabilities

* revert batch job test

* revert formatting changes

* pr feedback

* pr feedback

* remove unused imports

* rename feature flag decorators

* pr feedback

Co-authored-by: Sebastian Rindom <skrindom@gmail.com>

packages/medusa/src/api/middlewares/feature-flag-enabled.ts

@@ -0,0 +1,18 @@
+import { NextFunction, Request, Response } from "express"
+import { FlagRouter } from "../../utils/flag-router"
+
+export function isFeatureFlagEnabled(
+  flagKey: string
+): (req: Request, res: Response, next: NextFunction) => Promise<void> {
+  return async (req: Request, res: Response, next: NextFunction) => {
+    const featureFlagRouter = req.scope.resolve(
+      "featureFlagRouter"
+    ) as FlagRouter
+
+    if (!featureFlagRouter.isFeatureEnabled(flagKey)) {
+      res.sendStatus(404)
+    } else {
+      next()
+    }
+  }
+}