removed auto_increment from session key id

Keys are to be generated by rust safely

server/migrations/2020-05-17-225334_sessions/up.sql

@@ -2,7 +2,7 @@
 -- NOTE: the expires column is not explicitly a date because the code required
     -- to make the DATE field work with diesel is ass and looks annoying
 CREATE TABLE IF NOT EXISTS `sessions` (
-    `id` bigint UNSIGNED NOT NULL auto_increment,
+    `id` bigint UNSIGNED NOT NULL,
     `secret` varchar(255) NOT NULL,
     `expires` bigint UNSIGNED NOT NULL,
     PRIMARY KEY(`id`)