fix: Prevent duplicate task keys in FindByIdsAsync (#233)

Author: Richard P. Field III

src/Redis.OM/Searching/RedisCollection.cs

@@ -465,7 +465,7 @@ public T Single(Expression<Func<T, bool>> expression)
         public async Task<IDictionary<string, T?>> FindByIdsAsync(IEnumerable<string> ids)
         {
             var tasks = new Dictionary<string, Task<T?>>();
-            foreach (var id in ids)
+            foreach (var id in ids.Distinct())
             {
                 tasks.Add(id, FindByIdAsync(id));
             }

test/Redis.OM.Unit.Tests/RediSearchTests/SearchFunctionalTests.cs

@@ -693,6 +693,31 @@ public async Task FindByIdsAsyncIds()
             Assert.Equal(37, people[ids[1]].Age);
         }
 
+        [Fact]
+        public async Task FindByIdsAsyncIdsWithDuplicatedIds()
+        {
+            var person1 = new Person() {Name = "Alice", Age = 51};
+            var person2 = new Person() {Name = "Bob", Age = 37};
+
+            var collection = new RedisCollection<Person>(_connection);
+
+            await collection.InsertAsync(person1);
+            await collection.InsertAsync(person2);
+
+            var ids = new string[] {person1.Id, person2.Id, person1.Id, person2.Id};
+
+            var people = await collection.FindByIdsAsync(ids);
+            Assert.NotNull(people[ids[0]]);
+            Assert.Equal(ids[0], people[ids[0]].Id);
+            Assert.Equal("Alice", people[ids[0]].Name);
+            Assert.Equal(51, people[ids[0]].Age);
+
+            Assert.NotNull(people[ids[1]]);
+            Assert.Equal(ids[1], people[ids[1]].Id);
+            Assert.Equal("Bob", people[ids[1]].Name);
+            Assert.Equal(37, people[ids[1]].Age);
+        }
+
         [Fact]
         public async Task FindByIdsAsyncKeys()
         {