Follows (#172)

* Follows initial

* Fix #171, Fix #170, Fix #169, Fix #164

* More work on follows

* Fix compile error

* Upgrade meili version, add follows to search

migrations/20210301041252_follows.sql

@@ -0,0 +1,9 @@
+CREATE TABLE mod_follows(
+    follower_id bigint REFERENCES users NOT NULL,
+    mod_id bigint REFERENCES mods NOT NULL,
+    created timestamptz DEFAULT CURRENT_TIMESTAMP NOT NULL,
+    PRIMARY KEY (follower_id, mod_id)
+);
+
+ALTER TABLE mods
+    ADD COLUMN follows integer NOT NULL default 0;