don't return tracked objects from the dbContext to avoid clients modifying objects which EF tracks (#21)

Author: hahn-kev

src/SIL.Harmony.Core/QueryHelpers.cs

@@ -6,7 +6,7 @@ public static class QueryHelpers
 {
     public static async Task<SyncState> GetSyncState(this IQueryable<CommitBase> commits)
     {
-        var dict = await commits.GroupBy(c => c.ClientId)
+        var dict = await commits.AsNoTracking().GroupBy(c => c.ClientId)
             .Select(g => new { ClientId = g.Key, DateTime = g.Max(c => c.HybridDateTime.DateTime) })
             .AsAsyncEnumerable()//this is so the ticks are calculated server side instead of the db
             .ToDictionaryAsync(c => c.ClientId, c => c.DateTime.ToUnixTimeMilliseconds());

src/SIL.Harmony/Db/CrdtRepository.cs

@@ -194,7 +194,7 @@ public IQueryable<T> GetCurrentObjects<T>() where T : class
     {
         if (_crdtConfig.Value.EnableProjectedTables)
         {
-            return _dbContext.Set<T>();
+            return _dbContext.Set<T>().AsNoTracking();
         }
         throw new NotSupportedException("GetCurrentObjects is not supported when not using projected tables");
     }