Database basic CRUD (#27)

* started schema

* db schemas beginning

* first db schema gen

* added sqlc generation with go generate and sqlite driver

* i think these dependencies are needed

* added IF NOT EXISTS to create and CRUD for each table

* fixed missing columns

* added missing field

* fixed code generation with sqlc

backend/database/sql/schemas/release_groups.sql

@@ -0,0 +1,6 @@
+CREATE TABLE IF NOT EXISTS release_groups (
+  id   int PRIMARY KEY,
+  name text    NOT NULL,
+  cover_art_id int NOT NULL,
+  FOREIGN KEY(cover_art_id) REFERENCES cover_art(id)
+);