Add support for application/x-pem-file MIME type

This patch adds support for serializing and deserializing data with the
application/x-pem-file MIME type as plain text.

Fixes: #244

Author: robin-nitrokey

src/main/resources/python/api_client.hbs

@@ -905,6 +905,8 @@ class OpenApiResponse(typing.Generic[T], JSONDetector, abc.ABC):
             elif content_type.startswith('multipart/form-data'):
                 body_data = cls.__deserialize_multipart_form_data(response)
                 content_type = 'multipart/form-data'
+            elif content_type == 'application/x-pem-file':
+                body_data = response.data.decode()
             else:
                 raise NotImplementedError('Deserialization of {} has not yet been implemented'.format(content_type))
             body_schema = schemas.get_class(body_schema)
@@ -1404,7 +1406,7 @@ class RequestBody(StyleFormSerializer, JSONDetector):
             if isinstance(cast_in_data, (schemas.FileIO, bytes)):
                 raise ValueError(f"Invalid input data type. Data must be int/float/str/bool/None/tuple/immutabledict and it was type {type(cast_in_data)}")
             return cls.__serialize_json(cast_in_data)
-        elif content_type == 'text/plain':
+        elif content_type in ['text/plain', 'application/x-pem-file']:
             if not isinstance(cast_in_data, (int, float, str)):
                 raise ValueError(f"Unable to serialize type {type(cast_in_data)} to text/plain")
             return cls.__serialize_text_plain(cast_in_data)