creating and deleting users

sql/schema/001_users.sql

@@ -3,7 +3,7 @@ CREATE TABLE users(
     id UUID PRIMARY KEY,
     created_at TIMESTAMP not null DEFAULT CURRENT_TIMESTAMP,
     updated_at TIMESTAMP not null DEFAULT CURRENT_TIMESTAMP,
-    email TEXT not null
+    email TEXT not null UNIQUE 
 );
 
 -- +goose Down