fix: populate default created_by and add not-null constraint in templates (#2290)

coderd/database/dump.sql

@@ -249,7 +249,7 @@ CREATE TABLE templates (
     description character varying(128) DEFAULT ''::character varying NOT NULL,
     max_ttl bigint DEFAULT '604800000000000'::bigint NOT NULL,
     min_autostart_interval bigint DEFAULT '3600000000000'::bigint NOT NULL,
-    created_by uuid
+    created_by uuid NOT NULL
 );
 
 CREATE TABLE users (