feat(admin-bundler,admin-vite-plugin,medusa): Add support for loading Admin Extensions from plugins (#10869)

Should not be merged before https://github.com/medusajs/medusa/pull/10895

**What**
- Introduces a new `plugin` command to `admin-bundler`, currently not used anywhere but will be called from `medusa build:plugin`
- Discovers plugins with extensions and add passes the to `admin-vite-plugin`.
- Updates `admin-vite-plugin` so its able to read built admin extensions.

Resolves CMRC-830, CMRC-839

packages/admin/admin-vite-plugin/src/utils.ts

@@ -14,6 +14,7 @@ import {
   type ExportNamedDeclaration,
   type NodePath,
   type ParserOptions,
+  type VariableDeclarator,
 } from "./babel"
 
 export function normalizePath(file: string) {
@@ -48,7 +49,7 @@ export function generateModule(code: string) {
   }
 }
 
-const VALID_FILE_EXTENSIONS = [".tsx", ".jsx"]
+export const VALID_FILE_EXTENSIONS = [".tsx", ".jsx", ".js"]
 
 /**
  * Crawls a directory and returns all files that match the criteria.
@@ -96,8 +97,25 @@ export async function crawl(
  * Extracts and returns the properties of a `config` object from a named export declaration.
  */
 export function getConfigObjectProperties(
-  path: NodePath<ExportNamedDeclaration>
+  path: NodePath<ExportNamedDeclaration | VariableDeclarator>
 ) {
+  if (isVariableDeclarator(path.node)) {
+    const configDeclaration = isIdentifier(path.node.id, { name: "config" })
+      ? path.node
+      : null
+
+    if (
+      configDeclaration &&
+      isCallExpression(configDeclaration.init) &&
+      configDeclaration.init.arguments.length > 0 &&
+      isObjectExpression(configDeclaration.init.arguments[0])
+    ) {
+      return configDeclaration.init.arguments[0].properties
+    }
+
+    return null
+  }
+
   const declaration = path.node.declaration
 
   if (isVariableDeclaration(declaration)) {
@@ -126,6 +144,30 @@ export async function hasDefaultExport(
     ExportDefaultDeclaration() {
       hasDefaultExport = true
     },
+    AssignmentExpression(path) {
+      if (
+        path.node.left.type === "MemberExpression" &&
+        path.node.left.object.type === "Identifier" &&
+        path.node.left.object.name === "exports" &&
+        path.node.left.property.type === "Identifier" &&
+        path.node.left.property.name === "default"
+      ) {
+        hasDefaultExport = true
+      }
+    },
+    ExportNamedDeclaration(path) {
+      const specifiers = path.node.specifiers
+      if (
+        specifiers?.some(
+          (s) =>
+            s.type === "ExportSpecifier" &&
+            s.exported.type === "Identifier" &&
+            s.exported.name === "default"
+        )
+      ) {
+        hasDefaultExport = true
+      }
+    },
   })
   return hasDefaultExport
 }