add log_metadata function

mpsd-software-environment.py

@@ -36,11 +36,33 @@ config_vars = {
         "logs/mpsd_spack_ver_toolchains_"
         f"{datetime.datetime.now().replace(microsecond=0).isoformat()}.log"
     ),
+    "metadata_tag_open": "!<meta>",
+    "metadata_tag_close": "</meta>!",
     # TODO: modify toolchains,mpsd_spack_ver when the variable is available
     "spack_environments_repo": "https://gitlab.gwdg.de/mpsd-cs/spack-environments.git",
 }
 
 
+def log_metadata(key: str, value: str) -> None:
+    """Log metadata to the log file.
+
+    This function logs metadata to the log file. The metadata is
+    enclosed in a tag, so that it can be easily found in the log file.
+    logging module is used to write the metadata to the log file.
+
+    Parameters
+    ----------
+    key : str
+        key of the metadata
+    value : str
+        value of the metadata
+    returns : None
+    """
+    logging.info(
+        f"{config_vars['metadata_tag_open']}{key}:{value}{config_vars['metadata_tag_close']}"
+    )
+
+
 def set_up_logging(loglevel="warning", filename=None):
     """Set up logging.