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/routes/adventures/[id]/+page.server.ts

@@ -20,22 +20,10 @@ export const load = (async (event) => {
 		};
 	} else {
 		let adventure = (await request.json()) as AdditionalAdventure;
-		let collection: Collection | null = null;
-
-		if (adventure.collection) {
-			let res2 = await fetch(`${endpoint}/api/collections/${adventure.collection}/`, {
-				headers: {
-					Cookie: `sessionid=${event.cookies.get('sessionid')}`
-				},
-				credentials: 'include'
-			});
-			collection = await res2.json();
-		}
 
 		return {
 			props: {
-				adventure,
-				collection
+				adventure
 			}
 		};
 	}

frontend/src/routes/adventures/[id]/+page.svelte

@@ -360,12 +360,18 @@
 												? `🌍 ${$t('adventures.public')}`
 												: `🔒 ${$t('adventures.private')}`}
 										</div>
-										{#if data.props.collection}
+										<!-- {#if data.props.collection}
 											<div class="badge badge-sm badge-outline">
 												📚 <a href="/collections/{data.props.collection.id}" class="link"
 													>{data.props.collection.name}</a
 												>
 											</div>
+										{/if} -->
+										{#if adventure.collections && adventure.collections.length > 0}
+											<div class="badge badge-sm badge-outline">
+												📚
+												<p>{adventure.collections.length} {$t('navbar.collections')}</p>
+											</div>
 										{/if}
 									</div>
 								</div>

frontend/src/routes/collections/[id]/+page.svelte

@@ -362,12 +362,21 @@
 		} else {
 			let adventure = event.detail;
 
+			// add the collection id to the adventure collections array
+			if (!adventure.collections) {
+				adventure.collections = [collection.id];
+			} else {
+				if (!adventure.collections.includes(collection.id)) {
+					adventure.collections.push(collection.id);
+				}
+			}
+
 			let res = await fetch(`/api/adventures/${adventure.id}/`, {
 				method: 'PATCH',
 				headers: {
 					'Content-Type': 'application/json'
 				},
-				body: JSON.stringify({ collection: collection.id.toString() })
+				body: JSON.stringify({ collections: adventure.collections })
 			});
 
 			if (res.ok) {
@@ -550,6 +559,7 @@
 		on:close={() => {
 			isShowingLinkModal = false;
 		}}
+		collectionId={collection.id}
 		on:add={addAdventure}
 	/>
 {/if}