UUIDv7: ctor accepts MonoTime as recommended by IETF

[denizzzka]

I think it's worth adding ability to use of monotonous clocks to create UUIDs

At least, timestampRandomUUID() should use monotonic clock as recommended by IETF

[dlang-bot]

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[denizzzka]

Silly idea: monotonic time is not tied to specific points in time, so it is not suitable for calculating absolute timestamps by itself