feat: added new commands

- added follow command
- added unfollow command
- following command
- introduced logged in user middleware

sql/queries/feeds.sql

@@ -12,3 +12,7 @@ RETURNING *;
 
 -- name: GetAllFeeds :many
 SELECT id, created_at, updated_at, name, url, user_id FROM feeds;
+
+-- name: GetFeedByUrl :one
+SELECT id, created_at, updated_at, name, url, user_id FROM feeds
+WHERE url = $1;