Implement a favourites-functionality

[WinterIsCoding23]

Value proposition As a user I want to be able to mark one or more movies as favourites - and un-mark them when they are not my favourites anymore

Description

Acceptance-criteria

• [x] Every movie marked as favourite is displayed immediately in the Watchlist
• [x] Every movie marked as favourite can be un-favoured and is automatically removed from the Watchlist
• [x] By clicking on the movies in the Watchlist the user is directed to the details page

Tasks

• [x] Create a favourite-button (heart)
• [x] Add a toggle-favourite-function
• [x] Create a mongoDB-collection for movies in Watchlist
• [x] Connect app to database
• [x] Create isFavorite-Boolean (movie marked for Watchlist or not)
• [x] GET value of isFavorite from mongoDB
• [x] POST/PUT updated value of isFavorite to mongoDB - depending on toggle-button
• [x] Watchlist: Change data-fetching from popular movies to favourite-marked movies
• [x] Make each movie in Watchlist clickable and lead it to Detailpage

[WinterIsCoding23]

• [x] Edit: Add favorite-button to every movie on detail-page
• [x] Edit: Add poster, title to mongoDB-collection
• [x] Edit: Fix error on Watchlist: After click on Watchlist-movie togglebutton shows "make favorite" & click on movie seemingly without effect on button and mongoDB
• [x] Bugfix in Watchlist-Slider: If poster_path empty, the placeholder-image is not shown and movie-element is out of place
• [x] Bugfix in ToggleFunction: Show "Loading..."-String while retrieving initial State from mongoDB
• [x] Bugfix in Watchlist: Show a RandomMovieOnWatchlist that actually is currently available for streaming