feat(utils): define file config (#13283)

** What
 - Allow auto-loaded Medusa files to export a config object.
 - Currently supports isDisabled to control loading.
 - new instance `FeatureFlag` exported by `@medusajs/framework/utils`
 - `feature-flags` is now a supported folder for medusa projects, modules, providers and plugins. They will be loaded and added to `FeatureFlag`

** Why
 - Enables conditional loading of routes, migrations, jobs, subscribers, workflows, and other files based on feature flags.

```ts
// /src/feature-flags

import { FlagSettings } from "@medusajs/framework/feature-flags"

const CustomFeatureFlag: FlagSettings = {
  key: "custom_feature",
  default_val: false,
  env_key: "FF_MY_CUSTOM_FEATURE",
  description: "Enable xyz",
}

export default CustomFeatureFlag
```

```ts
// /src/modules/my-custom-module/migration/Migration20250822135845.ts

import { FeatureFlag } from "@medusajs/framework/utils"

export class Migration20250822135845 extends Migration {
  override async up(){ }
  override async down(){ }
}

defineFileConfig({
  isDisabled: () => !FeatureFlag.isFeatureEnabled("custom_feature")
})
```

packages/core/utils/src/modules-sdk/__tests__/mikro-orm-cli-config-builder.spec.ts

@@ -1,3 +1,4 @@
+import { CustomDBMigrator } from "../../dal/mikro-orm/custom-db-migrator"
 import { defineMikroOrmCliConfig } from "../mikro-orm-cli-config-builder"
 
 const moduleName = "myTestService"
@@ -28,6 +29,7 @@ describe("defineMikroOrmCliConfig", () => {
         generator: expect.any(Function),
         snapshotName: ".snapshot-medusa-my-test",
       },
+      extensions: [CustomDBMigrator],
     })
   })
 
@@ -47,6 +49,7 @@ describe("defineMikroOrmCliConfig", () => {
         generator: expect.any(Function),
         snapshotName: ".snapshot-medusa-my-test",
       },
+      extensions: [CustomDBMigrator],
     })
   })
 })

packages/core/utils/src/modules-sdk/migration-scripts/seed.ts

@@ -2,9 +2,9 @@ import { LoaderOptions, Logger, ModulesSdkTypes } from "@medusajs/types"
 import { EntitySchema } from "@mikro-orm/core"
 import { EOL } from "os"
 import { resolve } from "path"
+import { dynamicImport, isFileSkipped } from "../../common"
 import { mikroOrmCreateConnection } from "../../dal"
 import { loadDatabaseConfig } from "../load-module-database-config"
-import { dynamicImport } from "../../common"
 
 /**
  * Utility function to build a seed script that will insert the seed data.
@@ -52,6 +52,10 @@ export function buildSeedScript({
       }
     )
 
+    if (isFileSkipped(dataSeed)) {
+      return
+    }
+
     const dbData = loadDatabaseConfig(moduleName, options)!
     const entities = Object.values(models) as unknown as EntitySchema[]
 

packages/core/utils/src/modules-sdk/mikro-orm-cli-config-builder.ts

@@ -7,7 +7,7 @@ import type {
 } from "@mikro-orm/core"
 import { defineConfig } from "@mikro-orm/postgresql"
 import { kebabCase } from "../common"
-import { CustomTsMigrationGenerator } from "../dal"
+import { CustomDBMigrator, CustomTsMigrationGenerator } from "../dal"
 import { DmlEntity, toMikroOrmEntities } from "../dml"
 
 type Options = Partial<Omit<MikroORMOptions, "entities" | "entitiesTs">> & {
@@ -65,5 +65,6 @@ export function defineMikroOrmCliConfig(
       generator: CustomTsMigrationGenerator,
       ...options.migrations,
     },
+    extensions: [CustomDBMigrator],
   }) as ReturnedOptions
 }