Add v5 Language endpoints

src/Sonarr.Api.V5/Localization/LanguageController.cs

@@ -0,0 +1,35 @@
+using Microsoft.AspNetCore.Mvc;
+using NzbDrone.Core.Languages;
+using Sonarr.Http;
+using Sonarr.Http.REST;
+
+namespace Sonarr.Api.V5.Localization;
+
+[V5ApiController]
+public class LanguageController : RestController<LanguageResource>
+{
+    protected override LanguageResource GetResourceById(int id)
+    {
+        var language = (Language)id;
+
+        return new LanguageResource
+        {
+            Id = (int)language,
+            Name = language.ToString()
+        };
+    }
+
+    [HttpGet]
+    public List<LanguageResource> GetAll()
+    {
+        var languageResources = Language.All.Select(l => new LanguageResource
+        {
+            Id = (int)l,
+            Name = l.ToString()
+        })
+                                .OrderBy(l => l.Id > 0).ThenBy(l => l.Name)
+                                .ToList();
+
+        return languageResources;
+    }
+}

src/Sonarr.Api.V5/Localization/LanguageResource.cs

@@ -0,0 +1,12 @@
+using System.Text.Json.Serialization;
+using Sonarr.Http.REST;
+
+namespace Sonarr.Api.V5.Localization;
+
+public class LanguageResource : RestResource
+{
+    [JsonIgnore(Condition = JsonIgnoreCondition.Never)]
+    public new int Id { get; set; }
+    public string? Name { get; set; }
+    public string? NameLower => Name?.ToLowerInvariant();
+}