Represents boundary behaviour for operations such as floating window. The type specifies whether incomplete windows (of smaller than required length) should be produced at the beginning (`AtBeginning`) or at the end (`AtEnding`) or skipped (`Skip`). For chunking, combinations are allowed too - to skip incomplete chunk at the beginning, use `Boundary.Skip ||| Boundary.AtBeginning`. [category:Parameters and results of various operations]

[SerializableAttribute]
[FlagsAttribute]
public enum Boundary