Add project files.

AS1024.GeoFeed/Controllers/GeofeedController.cs

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+using Microsoft.AspNetCore.Mvc;
+using AS1024.GeoFeed.Interfaces;
+using AS1024.GeoFeed.GeoFeedBuilder;
+using Microsoft.Extensions.Caching.Memory;
+using AS1024.GeoFeed.Models;
+using System.Text;
+
+namespace AS1024.GeoFeed.Controllers
+{
+    [ApiController]
+    [Route("[controller]")]
+    [Route("[controller].csv")]
+
+    public class GeofeedController : ControllerBase
+    {
+        private readonly IGeoFeedProvider builder;
+        private readonly IMemoryCache memoryCache;
+        private const string GeoFeedCacheKey = "GeoFeedData";
+
+        public GeofeedController(IGeoFeedProvider builder,
+            IMemoryCache memoryCache) {
+            this.builder = builder;
+            this.memoryCache = memoryCache;
+        }
+
+        [HttpGet]
+        [Route("")]
+        public async Task<IActionResult> Get()
+        {
+            if (!memoryCache.TryGetValue(GeoFeedCacheKey, out List<IPGeoFeed>? feed))
+            {
+                feed = await builder.GetGeoFeedData();
+                var cacheEntryOptions = new MemoryCacheEntryOptions()
+                    .SetAbsoluteExpiration(TimeSpan.FromHours(1));
+                memoryCache.Set(GeoFeedCacheKey, feed, cacheEntryOptions);
+            }
+
+            var csvContent = feed.ToGeoFeedCsv(); // Assuming ToGeoFeedCsv() returns a string in CSV format.
+            var contentBytes = Encoding.UTF8.GetBytes(csvContent);
+            var contentType = "text/csv";
+
+            return new FileContentResult(contentBytes, contentType)
+            {
+                FileDownloadName = "geofeed.csv"
+            };
+        }
+    }
+}