docs: add new troubleshooting section for create-medusa-app (#6071)

* docs: add new troubleshooting section for create-medusa-app

* small fixes

www/apps/docs/content/create-medusa-app.mdx

@@ -18,6 +18,7 @@ import EaddrinuseSection from './troubleshooting/eaddrinuse.md'
 import InvalidTokenError from './troubleshooting/create-medusa-app-errors/_no-browser-token-error.md'
 import PostgresDockerError from './troubleshooting/database-errors/_docker.md'
 import DbUrlError from './troubleshooting/create-medusa-app-errors/_db-url-error.md'
+import PortError from './troubleshooting/create-medusa-app-errors/_port.md'
 
 # Install Medusa with create-medusa-app
 
@@ -218,6 +219,10 @@ Based on what you're building, you can find a development path for you in the Re
 
 <DetailsList
   sections={[
+    {
+      title: "Admin Login or User Errors",
+      content: <PortError />
+    },
     {
       title: 'Can\'t connect to database with --db-url option',
       content: <DbUrlError />

www/apps/docs/content/troubleshooting/create-medusa-app-errors.mdx

@@ -7,6 +7,7 @@ import OtherErrors from './create-medusa-app-errors/_other-errors.mdx'
 import InvalidTokenError from './create-medusa-app-errors/_no-browser-token-error.md'
 import DockerSection from "./database-errors/_docker.md"
 import DbUrlError from './create-medusa-app-errors/_db-url-error.md'
+import PortError from './create-medusa-app-errors/_port.md'
 
 ## TypeError: cmd is not a function
 
@@ -14,6 +15,12 @@ import DbUrlError from './create-medusa-app-errors/_db-url-error.md'
 
 ---
 
+## Admin Login or User Errors
+
+<PortError />
+
+---
+
 ## Invalid Token Error with --no-browser Option
 
 <InvalidTokenError />

www/apps/docs/content/troubleshooting/create-medusa-app-errors/_port.md

@@ -0,0 +1,10 @@
+By default, the Medusa backend runs on `localhost:9000`. However, the port may change based on the `PORT` environment variable.
+
+If you run the `create-medusa-app` command, and the installation finishes successfully, but the backend runs on a different port than `9000`, it may cause errors when you try to create an admin user or login during the onboarding process. This could either be because you have the `PORT` environment variable set to something differnt, or because of port forwarding.
+
+To resolve this, you must:
+
+1. Terminate the `create-medusa-app` process and change to the new backend's directory.
+2. Either explicitely set the `PORT` environment variable to `9000`, or set the environment variable `MEDUSA_ADMIN_BACKEND_URL` to the backend's URL. For example, if the backend is running on `localhost:7000`, change the `MEDUSA_ADMIN_BACKEND_URL` to `http://localhost:7001`. This ensures that the admin uses the correct port. In case of port fowarding, it's recommended to explicitely set the `PORT` environment variable.
+3. Create an admin user using the [user command of the CLI tool](../../cli/reference.mdx#user).
+4. Start the backend again either with the `dev` command of the backend project or using `npx medusa develop` and try to login again.