Add the basic sqlalchemy code

database.py

@@ -0,0 +1,27 @@
+from sqlalchemy import Table, Column, BigInteger, Numeric, String, Text, MetaData, ForeignKey
+import decimal
+
+# Create a metadata object containing info about the tables in the database
+metadata = MetaData()
+
+# Metadata for the users table
+# TODO: maybe add a 'credit' column
+users = Table("users", metadata,
+              Column("telegram_user_id", BigInteger, primary_key=True),
+              Column("first_name", String, nullable=False),
+              Column("last_name", String),
+              Column("username", String))
+
+# Metadata for the admins table
+# TODO: add columns for all the possible permissions
+admins = Table("admins", metadata,
+               Column("telegram_user_id", ForeignKey("users.telegram_user_id"), primary_key=True))
+
+# Metadata for the products table
+products = Table("products", metadata,
+                 Column("product_name", String, primary_key=True),
+                 Column("description", Text),
+                 Column("price", Numeric(...)))
+
+#TODO: many things are still missing...
+raise NotImplementedError()