add aurweb.models.session.Session ORM database object

+ Added aurweb.util module.
    - Added make_random_string function.
+ Added aurweb.db.make_random_value function.
    - Takes a model and a column and introspects them to figure out the
      proper column length to create a random string for; then creates
      a unique string for that column.

Signed-off-by: Kevin Morris <kevr@0cost.org>

aurweb/util.py

@@ -0,0 +1,7 @@
+import random
+import string
+
+
+def make_random_string(length):
+    return ''.join(random.choices(string.ascii_lowercase +
+                                  string.digits, k=length))