feat(config): Read secrets from .env file and environemnt variables (#109)

Config variables used to connect to our two databased can now also be
ingested from the local environment variables. Such variables can also
be passed in using a `.env` file as described in the README.md

tests/config/config_providers_test.py

@@ -3,7 +3,10 @@ from unittest.mock import mock_open, patch
 
 import pytest
 
-from aki_prj23_transparenzregister.config.config_providers import JsonFileConfigProvider
+from aki_prj23_transparenzregister.config.config_providers import (
+    EnvironmentConfigProvider,
+    JsonFileConfigProvider,
+)
 
 
 def test_json_provider_init_fail() -> None:
@@ -72,3 +75,49 @@ def test_json_provider_get_mongo() -> None:
             assert config.hostname == data["mongo"]["host"]
             assert config.database == data["mongo"]["database"]
             assert config.port == data["mongo"]["port"]
+
+
+def test_env_provider_constructor() -> None:
+    with patch("aki_prj23_transparenzregister.config.config_providers.os") as mock_os:
+        keys = {"PYTHON_TEST": "test", "NOT_PYTHON_TEST": ""}
+        mock_os.environ = keys
+        provider = EnvironmentConfigProvider()
+        assert provider.__data__ == {"TEST": "test"}
+
+
+def test_env_provider_postgres() -> None:
+    provider = EnvironmentConfigProvider()
+    env_data = {
+        "POSTGRES_USERNAME": "postgres",
+        "POSTGRES_PASSWORD": "postgres",
+        "POSTGRES_HOST": "localhost",
+        "POSTGRES_DATABASE": "postgres",
+        "POSTGRES_PORT": "5432",
+    }
+    provider.__data__ = env_data
+    conn_string = provider.get_postgre_connection_string()
+
+    assert conn_string.database == env_data["POSTGRES_DATABASE"]
+    assert conn_string.host == env_data["POSTGRES_HOST"]
+    assert conn_string.password == env_data["POSTGRES_PASSWORD"]
+    assert conn_string.port == env_data["POSTGRES_PORT"]
+    assert conn_string.username == env_data["POSTGRES_USERNAME"]
+
+
+def test_env_provider_mongodb() -> None:
+    provider = EnvironmentConfigProvider()
+    env_data = {
+        "MONGO_USERNAME": "username",
+        "MONGO_HOST": "localhost",
+        "MONGO_PASSWORD": "password",
+        "MONGO_PORT": 27017,
+        "MONGO_DATABASE": "transparenzregister",
+    }
+    provider.__data__ = env_data
+    conn_string = provider.get_mongo_connection_string()
+
+    assert conn_string.database == env_data["MONGO_DATABASE"]
+    assert conn_string.hostname == env_data["MONGO_HOST"]
+    assert conn_string.password == env_data["MONGO_PASSWORD"]
+    assert conn_string.port == env_data["MONGO_PORT"]
+    assert conn_string.username == env_data["MONGO_USERNAME"]