Split raw database connections out of aurweb.db

The aurweb-git-auth script does not need any ORM functionality, only access to the raw database connection. We can avoid the (~0.5s) time penalty of importing aurweb.db, by splitting the raw connection part into a separate aurweb.db_connection module.

Fixes: #374 (closed)

aurweb/git/auth.py

@@ -5,7 +5,7 @@ import shlex
 import sys
 
 import aurweb.config
-import aurweb.db
+import aurweb.db_connection
 
 
 def format_command(env_vars, command, ssh_opts, ssh_key):
@@ -34,7 +34,7 @@ def main():
     if keytype not in valid_keytypes:
         exit(1)
 
-    conn = aurweb.db.Connection()
+    conn = aurweb.db_connection.Connection()
 
     cur = conn.execute("SELECT Users.Username, Users.AccountTypeID FROM Users "
                        "INNER JOIN SSHPubKeys ON SSHPubKeys.UserID = Users.ID "