start adding arg parse to make it extendable

main.py

@@ -1,6 +1,17 @@
+import pathlib
+
 import ijson
 import sqlite3
 import pandas as pd
+import argparse
+
+parser = argparse.ArgumentParser()
+parser.add_argument("-i", "--input", help="folder containing input json(s)", required=True, type=pathlib.Path)
+parser.add_argument("-o", "--output", help="folder to place csv", required=True, type=pathlib.Path)
+parser.add_argument("-s", "--single", action="store_true", help="merge all json files to single output csv")
+parser.add_argument("-j", "--join-column", help="join column from top-level to merge nested json", required=True)
+parser.add_argument("-m", "--metadata", type=int, help="how many records to parse for building metadata", default=100)
+parser.parse_args()
 
 flat_keys = ["cost_center", "location", "customer"]
 extract_keys = {