Multiple image URLs (#4000)

* Backend changes - ported from scene impl
* Front end changes
* Refactor URL mutation code

pkg/sqlite/migrations/50_image_urls.up.sql

@@ -0,0 +1,70 @@
+PRAGMA foreign_keys=OFF;
+
+CREATE TABLE `image_urls` (
+  `image_id` integer NOT NULL,
+  `position` integer NOT NULL,
+  `url` varchar(255) NOT NULL,
+  foreign key(`image_id`) references `images`(`id`) on delete CASCADE,
+  PRIMARY KEY(`image_id`, `position`, `url`)
+);
+
+CREATE INDEX `image_urls_url` on `image_urls` (`url`);
+
+-- drop url
+CREATE TABLE "images_new" (
+  `id` integer not null primary key autoincrement,
+  `title` varchar(255),
+  `rating` tinyint,
+  `studio_id` integer,
+  `o_counter` tinyint not null default 0,
+  `organized` boolean not null default '0',
+  `created_at` datetime not null,
+  `updated_at` datetime not null, 
+  `date` date,
+  foreign key(`studio_id`) references `studios`(`id`) on delete SET NULL
+);
+
+INSERT INTO `images_new`
+  (
+    `id`,
+    `title`,
+    `rating`,
+    `studio_id`,
+    `o_counter`,
+    `organized`,
+    `created_at`,
+    `updated_at`,
+    `date`
+  )
+  SELECT 
+    `id`,
+    `title`,
+    `rating`,
+    `studio_id`,
+    `o_counter`,
+    `organized`,
+    `created_at`,
+    `updated_at`,
+    `date`
+  FROM `images`;
+
+INSERT INTO `image_urls`
+  (
+    `image_id`,
+    `position`,
+    `url`
+  )
+  SELECT 
+    `id`,
+    '0',
+    `url`
+  FROM `images`
+  WHERE `images`.`url` IS NOT NULL AND `images`.`url` != '';
+
+DROP INDEX `index_images_on_studio_id`;
+DROP TABLE `images`;
+ALTER TABLE `images_new` rename to `images`;
+
+CREATE INDEX `index_images_on_studio_id` on `images` (`studio_id`);
+
+PRAGMA foreign_keys=ON;