Add endpoint for retrieveing the configured default language (#16086)

* Add endpoint for retrieveing the configured default language

* Update OpenApi.json

src/Umbraco.Cms.Api.Management/Controllers/Language/Item/DefaultLanguageEntityController.cs

@@ -0,0 +1,36 @@
+using Asp.Versioning;
+using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.Mvc;
+using Umbraco.Cms.Api.Management.ViewModels.Language.Item;
+using Umbraco.Cms.Core.Mapping;
+using Umbraco.Cms.Core.Models;
+using Umbraco.Cms.Core.Services;
+using Umbraco.Cms.Core.Services.OperationStatus;
+
+namespace Umbraco.Cms.Api.Management.Controllers.Language.Item;
+
+[ApiVersion("1.0")]
+public class DefaultLanguageEntityController : LanguageEntityControllerBase
+{
+    private readonly ILanguageService _languageService;
+    private readonly IUmbracoMapper _mapper;
+
+    public DefaultLanguageEntityController(ILanguageService languageService, IUmbracoMapper mapper)
+    {
+        _languageService = languageService;
+        _mapper = mapper;
+    }
+
+    [HttpGet("default")]
+    [MapToApiVersion("1.0")]
+    [ProducesResponseType(typeof(LanguageItemResponseModel), StatusCodes.Status200OK)]
+    public async Task<IActionResult> Default(CancellationToken cancellationToken)
+    {
+        ILanguage? language = await _languageService.GetDefaultLanguageAsync();
+        return language is not null
+            ? Ok(_mapper.Map<ILanguage, LanguageItemResponseModel>(language))
+            : OperationStatusResult(
+                LanguageOperationStatus.NotFound,
+                problemDetailsBuilder => NotFound(problemDetailsBuilder.WithTitle("The default language could not be found.")));
+    }
+}

src/Umbraco.Cms.Api.Management/OpenApi.json

@@ -11419,6 +11419,41 @@
         ]
       }
     },
+    "/umbraco/management/api/v1/item/language/default": {
+      "get": {
+        "tags": [
+          "Language"
+        ],
+        "operationId": "GetItemLanguageDefault",
+        "responses": {
+          "200": {
+            "description": "Success",
+            "content": {
+              "application/json": {
+                "schema": {
+                  "oneOf": [
+                    {
+                      "$ref": "#/components/schemas/LanguageItemResponseModel"
+                    }
+                  ]
+                }
+              }
+            }
+          },
+          "401": {
+            "description": "The resource is protected and requires an authentication token"
+          },
+          "403": {
+            "description": "The authenticated user do not have access to this resource"
+          }
+        },
+        "security": [
+          {
+            "Backoffice User": [ ]
+          }
+        ]
+      }
+    },
     "/umbraco/management/api/v1/language": {
       "get": {
         "tags": [

src/Umbraco.Core/Services/ILanguageService.cs

@@ -14,6 +14,14 @@ public interface ILanguageService
     /// </returns>
     Task<ILanguage?> GetAsync(string isoCode);
 
+    /// <summary>
+    ///     Gets the default <see cref="ILanguage" />
+    /// </summary>
+    /// <returns>
+    ///     <see cref="ILanguage" />
+    /// </returns>
+    Task<ILanguage?> GetDefaultLanguageAsync();
+
     /// <summary>
     ///     Gets the default language ISO code.
     /// </summary>

src/Umbraco.Core/Services/LanguageService.cs

@@ -42,6 +42,15 @@ internal sealed class LanguageService : RepositoryService, ILanguageService
         }
     }
 
+    /// <inheritdoc />
+    public async Task<ILanguage?> GetDefaultLanguageAsync()
+    {
+        using (ScopeProvider.CreateCoreScope(autoComplete: true))
+        {
+            return await Task.FromResult(_languageRepository.GetByIsoCode(_languageRepository.GetDefaultIsoCode()));
+        }
+    }
+
     /// <inheritdoc />
     public async Task<string> GetDefaultIsoCodeAsync()
     {