feat(database): scrape history

- added migration

pkg/database/migrations/004_scrape_history.sql

@@ -0,0 +1,11 @@
+-- +migrate Up
+CREATE TABLE "ScrapeHistory"
+(
+    user_source_id CHAR(25)  NOT NULL REFERENCES "UserSource" (id),
+    scrape_task_id CHAR(25) PRIMARY KEY,
+    created_at     TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    finished_at    TIMESTAMP NULL,
+    error          TEXT      NULL,
+    added_posts    INT       NOT NULL,
+    deleted_posts  INT       NOT NULL
+);