Move "rebuild_thumbnails" to being a management command

- Does not run every time the server reboots
- Has to be called manually
- Normally does not need to be run and is a long-running process!

InvenTree/company/apps.py

@@ -23,29 +23,4 @@ class CompanyConfig(AppConfig):
         This function is called whenever the Company app is loaded.
         """
 
-        if canAppAccessDatabase():
-            self.generate_company_thumbs()
-
-    def generate_company_thumbs(self):
-
-        from .models import Company
-
-        logger.debug("Checking Company image thumbnails")
-
-        try:
-            for company in Company.objects.all():
-                if company.image:
-                    url = company.image.thumbnail.name
-                    loc = os.path.join(settings.MEDIA_ROOT, url)
-
-                    if not os.path.exists(loc):
-                        logger.info("InvenTree: Generating thumbnail for Company '{c}'".format(c=company.name))
-                        try:
-                            company.image.render_variations(replace=False)
-                        except FileNotFoundError:
-                            logger.warning(f"Image file '{company.image}' missing")
-                        except UnidentifiedImageError:
-                            logger.warning(f"Image file '{company.image}' is invalid")
-        except (OperationalError, ProgrammingError):
-            # Getting here probably meant the database was in test mode
-            pass
+        pass