feat: Enhance Adventure and Collection Management

- Added support for multiple collections in AdventureSerializer, allowing adventures to be linked to multiple collections.
- Implemented validation to ensure collections belong to the current user during adventure creation and updates.
- Introduced a signal to update adventure publicity based on the public status of linked collections.
- Updated file permission checks to consider multiple collections when determining access rights.
- Modified AdventureImageViewSet and AttachmentViewSet to check access against collections instead of a single collection.
- Enhanced AdventureViewSet to support filtering and sorting adventures based on collections.
- Updated frontend components to manage collections more effectively, including linking and unlinking adventures from collections.
- Adjusted API endpoints and data structures to accommodate the new collections feature.
- Improved user experience with appropriate notifications for collection actions.

frontend/src/lib/components/AdventureLink.svelte

@@ -12,21 +12,31 @@
 	let isLoading: boolean = true;
 
 	export let user: User | null;
+	export let collectionId: string;
 
 	onMount(async () => {
 		modal = document.getElementById('my_modal_1') as HTMLDialogElement;
 		if (modal) {
 			modal.showModal();
 		}
-		let res = await fetch(`/api/adventures/all/?include_collections=false`, {
+		let res = await fetch(`/api/adventures/all/?include_collections=true`, {
 			method: 'GET'
 		});
 
 		const newAdventures = await res.json();
 
-		if (res.ok && adventures) {
+		// Filter out adventures that are already linked to the collections
+		// basically for each adventure, check if collections array contains the id of the current collection
+		if (collectionId) {
+			adventures = newAdventures.filter((adventure: Adventure) => {
+				// adventure.collections is an array of ids, collectionId is a single id
+				return !(adventure.collections ?? []).includes(collectionId);
+			});
+		} else {
 			adventures = newAdventures;
 		}
+
+		// No need to reassign adventures to newAdventures here, keep the filtered result
 		isLoading = false;
 	});