fix: QP Qualities are now a Replace instead of Add

Qualities are very high-stakes: They are error prone to modify across
multiple configuration files. The user is not able to control ordering
that way. To reduce the chances of users shooting themselves in the
foot, we only allow 1 file to uniformly set qualities.

CHANGELOG.md

@@ -13,6 +13,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Print error information about HTTP 401 instead of "Unable to determine".
 - Improved wording of remote service error messages.
 
+### Changed
+
+- `qualities` (inside `quality_profiles`) is now a "Replace" merge operation instead of "Add". This
+  means only one YAML file manages the full list of qualities. Either an include does it, or you
+  override the full list in your configuration file. There is no longer any combination.
+
 ## [5.4.1] - 2023-09-12
 
 ### Fixed

src/Recyclarr.TrashLib.Config/Parsing/PostProcessing/ConfigMerging/ServiceConfigMerger.cs

@@ -80,7 +80,7 @@ public abstract class ServiceConfigMerger<T> where T : ServiceConfigYaml
                     .Distinct(StringComparer.InvariantCultureIgnoreCase)
                     .ToList()))
             }),
-            Qualities = Combine(a.Qualities, b.Qualities, (a1, b1) => a1.Concat(b1).ToList())
+            Qualities = b.Qualities ?? a.Qualities
         };
     }
 }

src/tests/Recyclarr.TrashLib.Config.Tests/Parsing/PostProcessing/ConfigMerging/ServiceConfigMergerTest.cs

@@ -498,12 +498,6 @@ public class ServiceConfigMergerTest
                     },
                     Qualities = new[]
                     {
-                        new QualityProfileQualityConfigYaml
-                        {
-                            Enabled = true,
-                            Name = "quality1",
-                            Qualities = new[] {"quality"}
-                        },
                         new QualityProfileQualityConfigYaml
                         {
                             Enabled = false,