Enable code coverage and upload OpenAPI spec.

Add basic test to write out the actual openapi spec.

tests/Jellyfin.Api.Tests/OpenApiSpecTests.cs

@@ -0,0 +1,42 @@
+using System.IO;
+using System.Reflection;
+using System.Text.Json;
+using System.Threading.Tasks;
+using MediaBrowser.Model.Branding;
+using Xunit;
+using Xunit.Abstractions;
+
+namespace MediaBrowser.Api.Tests
+{
+    public sealed class OpenApiSpecTests : IClassFixture<JellyfinApplicationFactory>
+    {
+        private readonly JellyfinApplicationFactory _factory;
+        private readonly ITestOutputHelper _outputHelper;
+
+        public OpenApiSpecTests(JellyfinApplicationFactory factory, ITestOutputHelper outputHelper)
+        {
+            _factory = factory;
+            _outputHelper = outputHelper;
+        }
+
+        [Fact]
+        public async Task GetSpec_ReturnsCorrectResponse()
+        {
+            // Arrange
+            var client = _factory.CreateClient();
+
+            // Act
+            var response = await client.GetAsync("/api-docs/openapi.json");
+
+            // Assert
+            response.EnsureSuccessStatusCode();
+            Assert.Equal("application/json; charset=utf-8", response.Content.Headers.ContentType.ToString());
+
+            // Write out for publishing
+            var responseBody = await response.Content.ReadAsStringAsync();
+            string outputPath = Path.GetFullPath(Path.Combine(Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location) ?? ".", "openapi.json"));
+            _outputHelper.WriteLine("Writing OpenAPI Spec JSON to '{0}'.", outputPath);
+            File.WriteAllText(outputPath, responseBody);
+        }
+    }
+}