Adding click statistics

closes #2

migrations/2021-02-09-175834_add_statistics/down.sql

@@ -0,0 +1,3 @@
+-- This file should undo anything in `up.sql`
+
+DROP TABLE clicks;

migrations/2021-02-09-175834_add_statistics/up.sql

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+-- Your SQL goes here
+
+CREATE TABLE clicks
+(
+    id INTEGER PRIMARY KEY NOT NULL,
+    link INT NOT NULL,
+    created_at TIMESTAMP NOT NULL,
+
+    FOREIGN KEY
+    (link)
+       REFERENCES links
+    (id)
+);