[DEV-3938] Backport spec-first#1191

I am fixing the mime type hell in the current codebase.

especifico/decorators/response.py

@@ -46,7 +46,7 @@ def validate_response(self, data, status_code, headers, url):
         response_definition = self.operation.response_definition(str(status_code), content_type)
         response_schema = self.operation.response_schema(str(status_code), content_type)
 
-        if self.is_json_schema_compatible(response_schema):
+        if self.is_json_schema_compatible(response_schema, content_type):
             v = ResponseBodyValidator(response_schema, validator=self.validator)
             try:
                 data = self.operation.json_loads(data)
@@ -69,7 +69,7 @@ def validate_response(self, data, status_code, headers, url):
                 raise NonConformingResponseHeaders(message=msg)
         return True
 
-    def is_json_schema_compatible(self, response_schema: dict) -> bool:
+    def is_json_schema_compatible(self, response_schema: dict, content_type: str) -> bool:
         """
         Verify if the specified operation responses are JSON schema
         compatible.
@@ -80,7 +80,7 @@ def is_json_schema_compatible(self, response_schema: dict) -> bool:
         """
         if not response_schema:
             return False
-        return all_json([self.mimetype]) or self.mimetype == "text/plain"
+        return all_json([content_type]) or content_type == "text/plain"
 
     def __call__(self, function):
         """