additional_data: commands: Add additional_data_tool

Create a little tool to run files through the additional_data generator.

Usage ./mange.py additional_data_tool example-grants.json

This will write/overwrite an `additional_data` object into the grant
object(s).

datastore/additional_data/management/commands/additional_data_tool.py

@@ -0,0 +1,31 @@
+import json
+
+from django.core.management.base import BaseCommand
+
+from additional_data.generator import AdditionalDataGenerator
+
+
+class Command(BaseCommand):
+    help = "Writes the additional_data object to ThreeSixtyGiving grant data JSON file"
+
+    def add_arguments(self, parser):
+        parser.add_argument(
+            type=str,
+            action="store",
+            dest="grants_file",
+            help="The JSON file that contains an array of ThreeSixtyGiving grant data",
+        )
+
+    def handle(self, *args, **options):
+
+        with open(options["grants_file"]) as grants_file:
+            grants_json = json.load(grants_file)
+
+            generator = AdditionalDataGenerator()
+
+            for grant in grants_json["grants"]:
+                additional_data = generator.create(grant)
+                grant["additional_data"] = additional_data
+
+            with open(options["grants_file"], "w") as grants_file:
+                json.dump(grants_json, grants_file, indent=2)