feat: allow fetching of country-flags

src/Covid19Api.Endpoints.Rest/V1/CountryStatisticsController.cs

@@ -2,9 +2,12 @@
 using System.Collections.Generic;
 using System.Threading.Tasks;
 using Covid19Api.Presentation.Response;
+using Covid19Api.UseCases.Abstractions.Queries.Countries;
 using Covid19Api.UseCases.Abstractions.Queries.CountryStatistics;
 using MediatR;
 using Microsoft.AspNetCore.Mvc;
+using Microsoft.Extensions.Primitives;
+using Microsoft.Net.Http.Headers;
 
 namespace Covid19Api.Endpoints.Rest.V1
 {
@@ -34,5 +37,18 @@ public Task<CountryStatisticDto> LoadLatestForCountryAsync(string country) =>
         [HttpGet("{country}/history")]
         public Task<IEnumerable<CountryStatisticDto>> LoadHistoryForCountryAsync(string country) =>
             this.mediator.Send(new LoadHistoricalCountryStatisticsForCountryQuery(country));
+
+        [HttpGet("{countryCode}/flag")]
+        public async Task<IActionResult> LoadFlagAsync(string countryCode)
+        {
+            var (image, mimeType) = await this.mediator.Send(new LoadCountryFlagQuery(countryCode));
+
+            return new FileContentResult(image, mimeType)
+            {
+                EnableRangeProcessing = true,
+                FileDownloadName = $"{countryCode.ToLowerInvariant()}_flag",
+                LastModified = DateTimeOffset.MinValue,
+            };
+        }
     }
 }

src/Covid19Api.Presentation/Response/ImageDto.cs

@@ -0,0 +1,6 @@
+using System.Collections;
+
+namespace Covid19Api.Presentation.Response
+{
+    public record ImageDto(byte[] Image, string MimeType);
+}

src/Covid19Api.UseCases.Abstractions/Queries/Countries/LoadCountryFlagQuery.cs

@@ -0,0 +1,16 @@
+using System;
+using Covid19Api.Presentation.Response;
+using Covid19Api.UseCases.Abstractions.Base;
+using Covid19Api.UseCases.Abstractions.Models;
+using MediatR;
+
+namespace Covid19Api.UseCases.Abstractions.Queries.Countries
+{
+    public record LoadCountryFlagQuery(string CountryCode) : IRequest<ImageDto>, ICacheableRequest
+    {
+        public CacheConfiguration GetCacheConfiguration()
+        {
+            return new CacheConfiguration($"country_flag{CountryCode.ToLowerInvariant()}", TimeSpan.FromDays(1));
+        }
+    }
+}