Add SupportsSavepoints property to NpgsqlTransaction (npgsql#4978)

Author: bigjonroberts

Npgsql.sln.DotSettings

@@ -123,6 +123,7 @@
 	<s:Boolean x:Key="/Default/UserDictionary/Words/=regtype/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/UserDictionary/Words/=resultset/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/UserDictionary/Words/=Roundtrips/@EntryIndexedValue">True</s:Boolean>
+	<s:Boolean x:Key="/Default/UserDictionary/Words/=savepoints/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/UserDictionary/Words/=sproc/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/UserDictionary/Words/=Subrange/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/UserDictionary/Words/=subtransaction/@EntryIndexedValue">True</s:Boolean>

src/Npgsql/NpgsqlTransaction.cs

@@ -356,6 +356,18 @@ public Task ReleaseAsync(string name, CancellationToken cancellationToken = defa
             return Release(name, true, cancellationToken);
     }
 
+    /// <summary>
+    /// Indicates whether this transaction supports database savepoints.
+    /// </summary>
+#if NET5_0_OR_GREATER
+    public override bool SupportsSavepoints
+#else
+    public bool SupportsSavepoints
+#endif
+    {
+        get => _connector.DatabaseInfo.SupportsTransactions;
+    }
+
     #endregion
 
     #region Dispose
@@ -500,4 +512,4 @@ internal void UnbindIfNecessary()
     }
 
     #endregion
-}
+}

src/Npgsql/PublicAPI.Shipped.txt

@@ -1741,6 +1741,7 @@ override Npgsql.NpgsqlTransaction.RollbackAsync(string! name, System.Threading.C
 override Npgsql.NpgsqlTransaction.RollbackAsync(System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) -> System.Threading.Tasks.Task!
 override Npgsql.NpgsqlTransaction.Save(string! name) -> void
 override Npgsql.NpgsqlTransaction.SaveAsync(string! name, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) -> System.Threading.Tasks.Task!
+override Npgsql.NpgsqlTransaction.SupportsSavepoints.get -> bool
 override Npgsql.PostgresException.GetObjectData(System.Runtime.Serialization.SerializationInfo! info, System.Runtime.Serialization.StreamingContext context) -> void
 override Npgsql.PostgresException.IsTransient.get -> bool
 override Npgsql.PostgresException.SqlState.get -> string!