feat(core): add Author and Series entities for hierarchical monitoring (#118)

* feat(db): add MediaType discriminator to Movies table

Adds foundation for multi-media support by:
- Adding MediaType column to Movies table (migration 244)
- Adding MediaType property to Movie entity, defaulting to Movie

Existing movies will have MediaType=1 (Movie) after migration.
This prepares for future Book and Audiobook media types.

Addresses Issue #1

* refactor(core): create MediaItem abstract base class

Extracts common properties from Movie into a new MediaItem base class:
- MediaType, Monitored, QualityProfileId
- Path, RootFolderPath, Added, Tags, LastSearchTime

Movie now inherits from MediaItem and implements abstract methods
GetTitle() and GetYear() while maintaining backward-compatible
Title/Year property accessors.

This prepares for Book and Audiobook entities that will share
the same base structure.

Addresses Issue #1

* feat(core): add Author and Series entities for hierarchical monitoring

Introduces hierarchical structure for books/audiobooks:
- Author entity: tracks authors with monitoring, quality profiles, paths
- Series entity: groups books/audiobooks by series, linked to Author
- MediaItem: adds AuthorId and SeriesId for hierarchy support
- Migration 245: creates Authors and Series tables, adds columns to Movies

This enables Author → Series → Item monitoring inheritance for
future book and audiobook support.

Addresses Issue #2

---------

Co-authored-by: admin <admin@ardentleatherworks.com>

src/NzbDrone.Core/Authors/Author.cs

@@ -0,0 +1,30 @@
+using System;
+using System.Collections.Generic;
+using NzbDrone.Core.Datastore;
+
+namespace NzbDrone.Core.Authors
+{
+    public class Author : ModelBase
+    {
+        public Author()
+        {
+            Tags = new HashSet<int>();
+        }
+
+        public string Name { get; set; }
+        public string SortName { get; set; }
+        public string Description { get; set; }
+        public string ForeignAuthorId { get; set; }
+        public bool Monitored { get; set; }
+        public string Path { get; set; }
+        public string RootFolderPath { get; set; }
+        public int QualityProfileId { get; set; }
+        public DateTime Added { get; set; }
+        public HashSet<int> Tags { get; set; }
+
+        public override string ToString()
+        {
+            return Name;
+        }
+    }
+}

src/NzbDrone.Core/Datastore/Migration/245_add_author_series_tables.cs

@@ -0,0 +1,36 @@
+using FluentMigrator;
+using NzbDrone.Core.Datastore.Migration.Framework;
+
+namespace NzbDrone.Core.Datastore.Migration
+{
+    [Migration(245)]
+    public class add_author_series_tables : NzbDroneMigrationBase
+    {
+        protected override void MainDbUpgrade()
+        {
+            Create.TableForModel("Authors")
+                .WithColumn("Name").AsString().NotNullable()
+                .WithColumn("SortName").AsString().Nullable()
+                .WithColumn("Description").AsString().Nullable()
+                .WithColumn("ForeignAuthorId").AsString().Nullable()
+                .WithColumn("Monitored").AsBoolean().WithDefaultValue(false)
+                .WithColumn("Path").AsString().Nullable()
+                .WithColumn("RootFolderPath").AsString().Nullable()
+                .WithColumn("QualityProfileId").AsInt32().WithDefaultValue(0)
+                .WithColumn("Added").AsDateTime().WithDefaultValue(System.DateTime.UtcNow)
+                .WithColumn("Tags").AsString().WithDefaultValue("[]");
+
+            Create.TableForModel("Series")
+                .WithColumn("Title").AsString().NotNullable()
+                .WithColumn("SortTitle").AsString().Nullable()
+                .WithColumn("Description").AsString().Nullable()
+                .WithColumn("ForeignSeriesId").AsString().Nullable()
+                .WithColumn("AuthorId").AsInt32().Nullable()
+                .WithColumn("Monitored").AsBoolean().WithDefaultValue(false);
+
+            Alter.Table("Movies")
+                .AddColumn("AuthorId").AsInt32().Nullable()
+                .AddColumn("SeriesId").AsInt32().Nullable();
+        }
+    }
+}

src/NzbDrone.Core/Datastore/TableMapping.cs

@@ -4,6 +4,7 @@
 using Dapper;
 using NzbDrone.Common.Reflection;
 using NzbDrone.Core.Authentication;
+using NzbDrone.Core.Authors;
 using NzbDrone.Core.AutoTagging.Specifications;
 using NzbDrone.Core.Blocklisting;
 using NzbDrone.Core.Configuration;
@@ -114,6 +115,10 @@ public static void Map()
             Mapper.Entity<MovieFile>("MovieFiles").RegisterModel()
                   .Ignore(f => f.Path);
 
+            Mapper.Entity<Author>("Authors").RegisterModel();
+
+            Mapper.Entity<NzbDrone.Core.Series.Series>("Series").RegisterModel();
+
             Mapper.Entity<Movie>("Movies").RegisterModel()
                   .Ignore(s => s.RootFolderPath)
                   .Ignore(s => s.Title)

src/NzbDrone.Core/MediaItems/MediaItem.cs

@@ -21,6 +21,9 @@ protected MediaItem()
         public HashSet<int> Tags { get; set; }
         public DateTime? LastSearchTime { get; set; }
 
+        public int? AuthorId { get; set; }
+        public int? SeriesId { get; set; }
+
         public abstract string GetTitle();
         public abstract int GetYear();
     }

src/NzbDrone.Core/Series/Series.cs

@@ -0,0 +1,19 @@
+using NzbDrone.Core.Datastore;
+
+namespace NzbDrone.Core.Series
+{
+    public class Series : ModelBase
+    {
+        public string Title { get; set; }
+        public string SortTitle { get; set; }
+        public string Description { get; set; }
+        public string ForeignSeriesId { get; set; }
+        public int? AuthorId { get; set; }
+        public bool Monitored { get; set; }
+
+        public override string ToString()
+        {
+            return Title;
+        }
+    }
+}