docs: adjust summary length of endpoints (#2188)

* change titles for admin apis

* adjusted titles for storefront apis

* added a note about length in contribution guidelines

* adjusted title for get customer endpoint

packages/medusa/src/api/routes/admin/auth/create-session.ts

@@ -10,7 +10,7 @@ import { validator } from "../../../../utils/validator"
 /**
  * @oas [post] /auth
  * operationId: "PostAuth"
- * summary: "Authenticate a User"
+ * summary: "User Login"
  * x-authenticated: false
  * description: "Logs a User in and authorizes them to manage Store settings."
  * parameters: