feat: add `OVERRIDE_PIP_INSTALL` environment variable

backend/open_webui/env.py

@@ -95,6 +95,8 @@ try:
 except importlib.metadata.PackageNotFoundError:
     pass
 
+OVERRIDE_PIP_INSTALL = os.environ.get("OVERRIDE_PIP_INSTALL")
+PIP_INSTALL = OVERRIDE_PIP_INSTALL if (OVERRIDE_PIP_INSTALL != None) else PIP_INSTALL
 
 if PIP_INSTALL:
     PACKAGE_DATA = {"version": importlib.metadata.version("open-webui")}