Use deepcopy to avoid modifying responses

Responses and parameters can be stored as
dictionary/list properties on View subclasses, or on
HTTP operation methods.
The LabThings apispec plugin includes these dictionaries in
the spec, and the Marshmallow plugin then modifies the
spec to reference schemas.

In unit testing, we build the API description multiple times
per run of Python, which means that the second time it's
built, the dictionaries have been modified and contain
only {"$ref": "#/components/schema/name"} instead of a Schema object.

This commit uses deepcopy so that the descriptions on the
classes/methods are not modified, and unit testing works again.

src/labthings/apispec/plugins.py

@@ -1,6 +1,7 @@
 import re
 
 from apispec import BasePlugin
+from copy import deepcopy
 
 from apispec.ext.marshmallow import (
     MarshmallowPlugin as _MarshmallowPlugin,
@@ -101,11 +102,11 @@ def spec_for_interaction(cls, interaction):
                     "parameters": [],
                 }
                 # Allow custom responses from the class, overridden by the method
-                d[method]["responses"].update(getattr(interaction, "responses", {}))
-                d[method]["responses"].update(getattr(prop, "responses", {}))
+                d[method]["responses"].update(deepcopy(getattr(interaction, "responses", {})))
+                d[method]["responses"].update(deepcopy(getattr(prop, "responses", {})))
                 # Allow custom parameters from the class & method
-                d[method]["parameters"].extend(getattr(interaction, "parameters", {}))
-                d[method]["parameters"].extend(getattr(prop, "parameters", {}))
+                d[method]["parameters"].extend(deepcopy(getattr(interaction, "parameters", {})))
+                d[method]["parameters"].extend(deepcopy(getattr(prop, "parameters", {})))
         return d
 
     @classmethod
@@ -148,10 +149,6 @@ def spec_for_property(cls, prop):
                 },
             )
 
-        # Enable custom responses from all methods
-        for method in d.keys():
-            d[method]["responses"].update(prop.responses)
-
         return d
 
     def spec_for_action(self, action):
@@ -245,8 +242,6 @@ def spec_for_action(self, action):
                 },
             },
         )
-        # Enable custom responses from POST
-        d["post"]["responses"].update(action.responses)
         return d
 
     @classmethod