feat: Option on item's page to add/remove from watchlist (#781)

* feat: adds button on the page of a media item to add or remove it from a user's watchlist

re #730

* fix: whitespace and i18n key

* style: fix code format to the required standards

* refactor: change axios for the fetch api

---------

Co-authored-by: JoaquinOlivero <joaquin.olivero@hotmail.com>

server/routes/tv.ts

@@ -1,7 +1,9 @@
 import RottenTomatoes from '@server/api/rating/rottentomatoes';
 import TheMovieDb from '@server/api/themoviedb';
 import { MediaType } from '@server/constants/media';
+import { getRepository } from '@server/datasource';
 import Media from '@server/entity/Media';
+import { Watchlist } from '@server/entity/Watchlist';
 import logger from '@server/logger';
 import { mapTvResult } from '@server/models/Search';
 import { mapSeasonWithEpisodes, mapTvDetails } from '@server/models/Tv';
@@ -19,7 +21,16 @@ tvRoutes.get('/:id', async (req, res, next) => {
 
     const media = await Media.getMedia(tv.id, MediaType.TV);
 
-    return res.status(200).json(mapTvDetails(tv, media));
+    const onUserWatchlist = await getRepository(Watchlist).exist({
+      where: {
+        tmdbId: Number(req.params.id),
+        requestedBy: {
+          id: req.user?.id,
+        },
+      },
+    });
+
+    return res.status(200).json(mapTvDetails(tv, media, onUserWatchlist));
   } catch (e) {
     logger.debug('Something went wrong retrieving series', {
       label: 'API',