First pass at cleaning entity classes.

- Documents all library entities
- Fixes styling warnings for library entities
- Updates library entities to inherit from interfaces
- Makes library entites no longer partial.

Jellyfin.Data/Interfaces/IHasArtwork.cs

@@ -0,0 +1,16 @@
+using System.Collections.Generic;
+using Jellyfin.Data.Entities.Libraries;
+
+namespace Jellyfin.Data.Interfaces
+{
+    /// <summary>
+    /// An interface abstracting an entity that has artwork.
+    /// </summary>
+    public interface IHasArtwork
+    {
+        /// <summary>
+        /// Gets a collection containing this entity's artwork.
+        /// </summary>
+        ICollection<Artwork> Artwork { get; }
+    }
+}

Jellyfin.Data/Interfaces/IHasCompanies.cs

@@ -0,0 +1,16 @@
+using System.Collections.Generic;
+using Jellyfin.Data.Entities.Libraries;
+
+namespace Jellyfin.Data.Interfaces
+{
+    /// <summary>
+    /// An abstraction representing an entity that has companies.
+    /// </summary>
+    public interface IHasCompanies
+    {
+        /// <summary>
+        /// Gets a collection containing this entity's companies.
+        /// </summary>
+        ICollection<Company> Companies { get; }
+    }
+}

Jellyfin.Data/Interfaces/IHasConcurrencyToken.cs

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+namespace Jellyfin.Data.Interfaces
+{
+    /// <summary>
+    /// An interface abstracting an entity that has a concurrency token.
+    /// </summary>
+    public interface IHasConcurrencyToken
+    {
+        /// <summary>
+        /// Gets the version of this row. Acts as a concurrency token.
+        /// </summary>
+        uint RowVersion { get; }
+
+        /// <summary>
+        /// Called when saving changes to this entity.
+        /// </summary>
+        void OnSavingChanges();
+    }
+}

Jellyfin.Data/Interfaces/IHasPermissions.cs

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+using System.Collections.Generic;
+using Jellyfin.Data.Entities;
+using Jellyfin.Data.Enums;
+
+namespace Jellyfin.Data
+{
+    /// <summary>
+    /// An abstraction representing an entity that has permissions.
+    /// </summary>
+    public interface IHasPermissions
+    {
+        /// <summary>
+        /// Gets a collection containing this entity's permissions.
+        /// </summary>
+        ICollection<Permission> Permissions { get; }
+
+        /// <summary>
+        /// Checks whether this entity has the specified permission kind.
+        /// </summary>
+        /// <param name="kind">The kind of permission.</param>
+        /// <returns><c>true</c> if this entity has the specified permission, <c>false</c> otherwise.</returns>
+        bool HasPermission(PermissionKind kind);
+
+        /// <summary>
+        /// Sets the specified permission to the provided value.
+        /// </summary>
+        /// <param name="kind">The kind of permission.</param>
+        /// <param name="value">The value to set.</param>
+        void SetPermission(PermissionKind kind, bool value);
+    }
+}

Jellyfin.Data/Interfaces/IHasReleases.cs

@@ -0,0 +1,16 @@
+using System.Collections.Generic;
+using Jellyfin.Data.Entities.Libraries;
+
+namespace Jellyfin.Data.Interfaces
+{
+    /// <summary>
+    /// An abstraction representing an entity that has releases.
+    /// </summary>
+    public interface IHasReleases
+    {
+        /// <summary>
+        /// Gets a collection containing this entity's releases.
+        /// </summary>
+        ICollection<Release> Releases { get; }
+    }
+}