Reasonable defaults, isolate tests, EOS_LOGGING_LEVEL, EOS_CONFIG_DIR

* Add EOS_CONFIG_DIR to set config dir (relative path to EOS_DIR or
   absolute path).
    - config_folder_path read-only
    - config_file_path read-only
 * Default values to support app start with empty config:
    - latitude/longitude (Berlin)
    - optimization_ev_available_charge_rates_percent (null, so model
      default value is used)
    - Enable Akkudoktor electricity price forecast (docker-compose).
 * Fix some endpoints (empty data, remove unused params, fix types).
 * cacheutil: Use cache dir. Closes #240
 * Support EOS_LOGGING_LEVEL environment variable to set log level.
 * tests: All tests use separate temporary config
    - Add pytest switch --check-config-side-effect to check user
      config file existence after each test. Will also fail if user config
      existed before test execution (but will only check after the test has
      run).
      Enable flag in github workflow.
    - Globally mock platformdirs in config module. Now no longer required
      to patch individually.
      Function calls to config instance (e.g. merge_settings_from_dict)
      were unaffected previously.
 * Set Berlin as default location (default config/docker-compose).

tests/test_loadakkudoktor.py

@@ -4,7 +4,6 @@ import numpy as np
 import pendulum
 import pytest
 
-from akkudoktoreos.config.config import get_config
 from akkudoktoreos.core.ems import get_ems
 from akkudoktoreos.measurement.measurement import MeasurementDataRecord, get_measurement
 from akkudoktoreos.prediction.loadakkudoktor import (
@@ -13,12 +12,9 @@ from akkudoktoreos.prediction.loadakkudoktor import (
 )
 from akkudoktoreos.utils.datetimeutil import compare_datetimes, to_datetime, to_duration
 
-config_eos = get_config()
-ems_eos = get_ems()
-
 
 @pytest.fixture
-def load_provider():
+def load_provider(config_eos):
     """Fixture to initialise the LoadAkkudoktor instance."""
     settings = {
         "load_provider": "LoadAkkudoktor",
@@ -112,6 +108,7 @@ def test_update_data(mock_load_data, load_provider):
     mock_load_data.return_value = np.random.rand(365, 2, 24)
 
     # Mock methods for updating values
+    ems_eos = get_ems()
     ems_eos.set_start_datetime(pendulum.datetime(2024, 1, 1))
 
     # Assure there are no prediction records