Collection item matching misses entries because children endpoint is called without includeGuids=1

[gerra95]

Plexyfin 0.6.2.0 correctly detects all items in some Plex collections, but only adds a subset to the Jellyfin collection.
For example, one item was missing from the created Jellyfin collection even though it existed in Plex, had correct TMDb/IMDb IDs in Jellyfin, and could be added manually.
Root cause appears to be that GetCollectionItems() calls Plex collection children endpoints without includeGuids=1. Plex then returns only the internal plex://... GUID, so Plexyfin falls back to title matching. Adding includeGuids=1&includeExternalMedia=1 to the collection item URLs fixed the issue locally.

Example XML call, without includeGuids=1:
curl "http://PLEX_HOST:32400/library/collections/COLLECTION_ID/children?X-Plex-Token=TOKEN"
Output:
<Video ratingKey="123" key="/library/metadata/123" guid="plex://movie/xxxxxxxxxxxxxxxxxxxx" type="movie" title="Example Movie" year="1988"> </Video>

Example XML call, with includeGuids=1:
curl "http://PLEX_HOST:32400/library/collections/COLLECTION_ID/children?includeGuids=1&includeExternalMedia=1&X-Plex-Token=TOKEN"
Output:
<Video ratingKey="123" key="/library/metadata/123" guid="plex://movie/xxxxxxxxxxxxxxxxxxxx" type="movie" title="Example Movie" year="1988"> <Guid id="imdb://tt0000000"/> <Guid id="tmdb://12345"/> <Guid id="tvdb://678"/> </Video>

Code fix:

In `Jellyfin.Plugin.Plexyfin/Plex/PlexClient.cs`, inside `GetCollectionItems()`, add `includeGuids=1&includeExternalMedia=1` to all collection item URL patterns.

Example:

var collectionQuery = $"includeGuids=1&includeExternalMedia=1&X-Plex-Token={_token}";

var urlPatterns = new List<Uri>
{
    new Uri(_baseUrl, $"library/collections/{collectionId}/children?{collectionQuery}"),
    new Uri(_baseUrl, $"library/metadata/{collectionId}/children?{collectionQuery}"),
    new Uri(_baseUrl, $"library/collections/{collectionId}/all?{collectionQuery}"),
    new Uri(_baseUrl, $"library/metadata/{collectionId}/items?{collectionQuery}"),
    new Uri(_baseUrl, $"library/collections/{collectionId}/items?{collectionQuery}")
};

After applying this locally, the missing collection items were matched and added correctly.

Versions:
Jellyfin: 10.11.8
Plexyfin: 0.6.2.0
Plex: 1.43.1.10611