feat: added new commands

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

sql/queries/follows.sql

@@ -0,0 +1,30 @@
+-- name: CreateFollow :one
+WITH inserted_follow as (
+  INSERT INTO follows (id, created_at, updated_at, feed_id, user_id)
+  VALUES (
+    $1,
+    $2,
+    $3,
+    $4,
+    $5
+  )
+  RETURNING *
+)
+SELECT inserted_follow.*,
+  feeds.name as feed_name,
+  users.name as user_name
+FROM inserted_follow
+INNER JOIN users
+  ON inserted_follow.user_id = users.id
+INNER JOIN feeds
+  ON inserted_follow.feed_id = feeds.id;
+
+-- name: GetFollowsForUser :many
+SELECT follows.*, feeds.name as feed_name FROM follows
+INNER JOIN feeds
+  ON follows.feed_id = feeds.id
+WHERE follows.user_id = $1;
+
+-- name: DeleteFollowForUser :exec
+DELETE FROM follows
+WHERE feed_id = $1 AND user_id = $2;