feat: create libretime_shared package (#1349)

* feat: create libretime_shared package

- We don't use pydantic.BaseSettings because of some
  incompatble loading behavior.

* fix: whitelist pydantic in pylintrc

* docs: update to new BaseConfig behavior

* docs: change confusing config filepath

shared/libretime_shared/config.py

@@ -0,0 +1,101 @@
+import sys
+from os import environ
+from pathlib import Path
+from typing import Any, Dict, Optional
+
+from loguru import logger
+
+# pylint: disable=no-name-in-module
+from pydantic import BaseModel, ValidationError
+from pydantic.fields import ModelField
+from yaml import YAMLError, safe_load
+
+DEFAULT_ENV_PREFIX = "LIBRETIME"
+
+
+# pylint: disable=too-few-public-methods
+class BaseConfig(BaseModel):
+    """
+    Read and validate the configuration from 'filepath' and os environment.
+
+    :param filepath: yaml configuration file to read from
+    :param env_prefix: prefix for the environment variable names
+    :returns: configuration class
+    """
+
+    def __init__(
+        self,
+        *,
+        env_prefix: str = DEFAULT_ENV_PREFIX,
+        filepath: Optional[Path] = None,
+    ) -> None:
+        file_values = self._load_file_values(filepath)
+        env_values = self._load_env_values(env_prefix)
+
+        try:
+            super().__init__(
+                **{
+                    **file_values,
+                    **env_values,
+                },
+            )
+        except ValidationError as error:
+            logger.critical(error)
+            sys.exit(1)
+
+    def _load_env_values(self, env_prefix: str) -> Dict[str, Any]:
+        return self._get_fields_from_env(env_prefix, self.__fields__)
+
+    def _get_fields_from_env(
+        self,
+        env_prefix: str,
+        fields: Dict[str, ModelField],
+    ) -> Dict[str, Any]:
+        result: Dict[str, Any] = {}
+
+        for field in fields.values():
+            env_name = (env_prefix + "_" + field.name).upper()
+
+            if field.is_complex():
+                result[field.name] = self._get_fields_from_env(
+                    env_name,
+                    field.type_.__fields__,
+                )
+            else:
+                if env_name in environ:
+                    result[field.name] = environ[env_name]
+
+        return result
+
+    # pylint: disable=no-self-use
+    def _load_file_values(
+        self,
+        filepath: Optional[Path] = None,
+    ) -> Dict[str, Any]:
+        if filepath is None:
+            return {}
+
+        try:
+            return safe_load(filepath.read_text(encoding="utf-8"))
+        except YAMLError as error:
+            logger.critical(error)
+            sys.exit(1)
+
+
+# pylint: disable=too-few-public-methods
+class Database(BaseModel):
+    host: str = "localhost"
+    port: int = 5432
+    name: str = "libretime"
+    user: str = "libretime"
+    password: str = "libretime"
+
+
+# pylint: disable=too-few-public-methods
+class RabbitMQ(BaseModel):
+    host: str = "localhost"
+    port: int = 5672
+    name: str = "libretime"
+    user: str = "libretime"
+    password: str = "libretime"
+    vhost: str = "/libretime"