update _load_stressmodel and tests

- remove up and gain_scale_factor from dict and set using update_rfunc_settings
- fix test the same way

pastas/io/base.py

@@ -142,7 +142,11 @@ def _load_stressmodel(ts, data):
 
     if "rfunc" in ts.keys():
         rfunc_class = ts["rfunc"].pop("class")  # Determine response class
-        ts["rfunc"] = getattr(ps.rfunc, rfunc_class)(**ts["rfunc"])
+        rfunc_up = ts["rfunc"].pop("up", None)  # get up value
+        rfunc_gsf = ts["rfunc"].pop("gain_scale_factor", None)  # get gain_scale_factor
+        rfunc = getattr(ps.rfunc, rfunc_class)(**ts["rfunc"])
+        rfunc.update_rfunc_settings(up=rfunc_up, gain_scale_factor=rfunc_gsf)
+        ts["rfunc"] = rfunc
 
     if "recharge" in ts.keys():
         recharge_class = ts["recharge"].pop("class")

tests/test_rfuncs.py

@@ -21,7 +21,10 @@ def test_to_dict_rfuncs(rfunc_name) -> None:
     # Create the exact same instance using to_dict
     data = rfunc1.to_dict()
     rfunc_class = data.pop("class")  # Determine response class
+    rfunc_up = data.pop("up", None)
+    rfunc_gsf = data.pop("gain_scale_factor", None)
     rfunc2 = getattr(ps.rfunc, rfunc_class)(**data)
+    rfunc2.update_rfunc_settings(up=rfunc_up, gain_scale_factor=rfunc_gsf)
 
     if rfunc_name == "HantushWellModel":
         rfunc1.set_distances(100.0)