Added feature to retrieve ID of aggregated source name in config file

This feature is the starting point for running gde-core. The user will specify (in the configuration file) the name of the aggregated exposure model they wish to run gde-core on, and the credentials of the GDE Tiles database. The Configuration class takes care of interpreting the parameters from the configuration file, using tools from the gde-importer. Then one of the methods of the DatabaseQueries class retrieves the aggregated_source_id of the aggregated exposure model, as stored in the aggregated_sources table of the GDE Tiles database.

This MR depends on https://git.gfz-potsdam.de/dynamicexposure/globaldynamicexposure/gde-importer/-/merge_requests/40 (splitting of the Configuration class of the gde-importer into Configuration and ConfigurationMethods).

\approve @fd

gdecore/configuration.py

+#!/usr/bin/env python3
+
+# Copyright (C) 2021:
+#   Helmholtz-Zentrum Potsdam Deutsches GeoForschungsZentrum GFZ
+#
+# This program is free software: you can redistribute it and/or modify it
+# under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or (at
+# your option) any later version.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero
+# General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program. If not, see http://www.gnu.org/licenses/.
+
+import logging
+from gdeimporter.tools.configuration_methods import ConfigurationMethods
+
+logger = logging.getLogger()
+
+
+class Configuration:
+    """This class handles the configuration parameters of the gde-core.
+
+    Attributes:
+        self.model_name (str):
+            Name of the input aggregated model.
+        self.database_gde_tiles (dict):
+            Dictionary containing the credentials needed to connect to the SQL database in which
+            information on the GDE tiles is stored. The exact parameters needed depend on the
+            database. They can be:
+                host (str):
+                    SQL database host address.
+                dbname (str):
+                    Name of the SQL database.
+                port (int):
+                    Port where the SQL database can be found.
+                username (str):
+                    User name to connect to the SQL database.
+                password (str):
+                    Password associated with self.username.
+    """
+
+    REQUIRES = [
+        "model_name",
+        "database_gde_tiles",
+    ]
+
+    def __init__(self, filepath, force_config_over_hierarchies=False):
+        """
+        Args:
+            filepath (str):
+                Full file path to the .yml configuration file.
+            force_config_over_hierarchies (bool):
+                If True, the contents of the .yml configuration file specified in filepath will
+                take precedence over any other hierarchy (e.g. preference of environment
+                variables if they exist). If False, hierarchies of preference established in
+                this class are applied. This parameter is used for forcing the testing of this
+                class under certain circumstances. Default: False.
+        """
+
+        config = ConfigurationMethods.read_config_file(filepath)
+
+        self.model_name = ConfigurationMethods.assign_parameter(config, "model_name")
+
+        self.database_gde_tiles = ConfigurationMethods.retrieve_database_credentials(
+            config, "database_gde_tiles", "test_db_gde_tiles.env", force_config_over_hierarchies
+        )
+
+        # Terminate if critical parameters are missing (not all parameters are critical)
+        for key_parameter in self.REQUIRES:
+            if getattr(self, key_parameter) is None:
+                error_message = (
+                    "Error: parameter '%s' could not be retrieved from "
+                    "configuration file. The program cannot run." % (key_parameter)
+                )
+                logger.critical(error_message)
+                raise OSError(error_message)