Fix Config.plugins_config - call model_post_init explicitly until pydantic 2.0 (#4858)

As per
https://github.com/pydantic/pydantic/issues/1729#issuecomment-1300576214,
the implementation of `model_post_init()` is postponed until Pydantic
v2. As a result, the initialization of PluginConfig is being skipped.

This fix calls `plugin.model_post_init()` explicitly.

The recency of the Pydantic v2 release means that some of the other
extensions we use do not support it yet. Specifically, extensions such
as spacy and openapi-python-client are currently limited to Pydantic
versions that are less than 2.0. There may be other extensions that have
the same limitation as well.

---------

Co-authored-by: Reinier van der Leer <github@pwuts.nl>

autogpt/config/config.py

@@ -83,6 +83,13 @@ class Config(SystemSettings):
     plugins: list[str]
     authorise_key: str
 
+    def __init__(self, **kwargs):
+        super().__init__(**kwargs)
+
+        # Hotfix: Call model_post_init explictly as it doesn't seem to be called for pydantic<2.0.0
+        # https://github.com/pydantic/pydantic/issues/1729#issuecomment-1300576214
+        self.model_post_init(**kwargs)
+
     # Executed immediately after init by Pydantic
     def model_post_init(self, **kwargs) -> None:
         if not self.plugins_config.plugins: