feat: Add config management module

This module is to set and read a config file where the main archive storage folder for planetarypy is determined.

src/planetarypy/config.py

@@ -0,0 +1,69 @@
+import logging
+from pathlib import Path
+
+import toml
+
+logger = logging.getLogger(__name__)
+
+# create configpath depending on package name
+pkg_name = __name__.split(".")[0]
+configpath = Path.home() / f".{pkg_name}.toml"
+
+
+def print_error():
+    print("No configuration file {} found.\n".format(configpath))
+    print(
+        """Please run `planetarypy.config.set_database_path('path_to_archive')` and provide
+        the path where `planetarypy` should archive all downloaded and created data."""
+    )
+    print(
+        f"`planetarypy` will store this path in {configpath}, where you can easily change it later."
+    )
+
+
+def set_database_path(dbfolder):
+    """Use to write the database path into the config.
+
+    Parameters
+    ----------
+    dbfolder: str or pathlib.Path
+        Path to where planetarypy will store data it downloads..
+    """
+    # First check if there's a config file, so that we don't overwrite
+    # anything:
+    try:
+        config = toml.load(str(configpath))
+    except IOError:  # config file doesn't exist
+        config = {}  # create new config dictionary
+
+    # check if there's an `data_archive` sub-dic
+    try:
+        archive_config = config["data_archive"]
+    except KeyError:
+        config["data_archive"] = {"path": dbfolder}
+    else:
+        archive_config["path"] = dbfolder
+
+    with open(configpath, "w") as f:
+        ret = toml.dump(config, f)
+    print(f"Saved database path {dbfolder} into {configpath}.")
+
+
+def get_data_root():
+    config = toml.load(str(configpath))
+    data_root = Path(config["data_archive"]["path"]).expanduser()
+    data_root.mkdir(exist_ok=True, parents=True)
+    return data_root
+
+
+if not configpath.exists():
+    print(f"No configuration file {configpath} found.\n")
+    savepath = input(
+        "Provide the path where all planetarypy-managed data should be stored:"
+    )
+    set_database_path(savepath)
+
+# get config object into module global
+config = toml.load(str(configpath))
+# get the archive path into module global
+data_root = get_data_root()