Filetype 10 not supported for oldext

[veenstrajelmer]

Describe the bug
When providing an old extfile with a polygon that prescribes the area in which a certain initial value is to be applied, it raises a ValidationError:

ValidationError: 1 validation error for ExtOldModel
oldext_invalid.ext -> forcing -> 0 -> FILETYPE
  value is not a valid enumeration member; permitted: 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 14 (type=type_error.enum; enum_values=[<ExtOldFileType.TimeSeries: 1>, <ExtOldFileType.TimeSeriesMagnitudeAndDirection: 2>, <ExtOldFileType.SpatiallyVaryingWindPressure: 3>, <ExtOldFileType.ArcInfo: 4>, <ExtOldFileType.SpiderWebData: 5>, <ExtOldFileType.CurvilinearData: 6>, <ExtOldFileType.Samples: 7>, <ExtOldFileType.TriangulationMagnitudeAndDirection: 8>, <ExtOldFileType.Polyline: 9>, <ExtOldFileType.NetCDFGridData: 11>, <ExtOldFileType.NetCDFWaveData: 14>])

To Reproduce
Create file oldext_insidepol.ext with these contents:

QUANTITY=frictioncoefficient
FILENAME=allcells.pli
FILETYPE=10
METHOD=4
OPERAND=O
VALUE=62.5

Run these lines:

import hydrolib.core.dflowfm as hcdfm
file_ext = "oldext_insidepol.ext"
hcdfm.ExtOldModel(file_ext)

Expected behavior
Support for filetype 10 (polygon) in old extfile. This is also defined in the extfile header

Version info (please complete the following information):

• OS: Windows
• Version 0.5.2