fix: support for cosmodb (#24)

Author: itsnotapt

backend/Tim.Backend/Providers/Database/MongoDbClient.cs

@@ -85,8 +85,9 @@ private async Task CreateCollectionAsync(string collectionName)
         private async Task CreateKustoExpireIndexKustoQueryRun(string collectionName)
         {
             var builder = Builders<KustoQueryRun>.IndexKeys;
+            var keys = m_configs.WithCosmosDb ? builder.Ascending("_ts") : builder.Ascending(x => x.ExecuteDateTimeUtc);
             var indexModel = new CreateIndexModel<KustoQueryRun>(
-                builder.Ascending(x => x.ExecuteDateTimeUtc),
+                keys,
                 new CreateIndexOptions
                 {
                     ExpireAfter = TimeSpan.FromDays(1),

backend/Tim.Backend/Startup/Config/MongoConfiguration.cs

@@ -33,6 +33,11 @@ public MongoConfiguration()
         [Required]
         public string DatabaseName { get; set; } = Environment.GetEnvironmentVariable("MONGO_DATABASE_NAME");
 
+        /// <summary>
+        /// Gets or sets a value indicating whether cosmosdb is being used.
+        /// </summary>
+        public bool WithCosmosDb { get; set; } = Environment.GetEnvironmentVariable("MONGO_WITH_COSMOSDB") == "true";
+
         /// <summary>
         /// Ensures that all required values are populated.
         /// </summary>