Person ID with leading zeroes

[robinmaisch]

A TA remarked that on the official documents by the faculty, his ID has a leading zero, which lead to an exception with the TimeSheetGenerator.
I was able to reproduce the following error message using the ID "0234567":

Invalid numeric value: Leading zeroes not allowed
 at [Source: REDACTED (`StreamReadFeature.INCLUDE_SOURCE_IN_LOCATION` disabled); line: 4, column: 14]

I would assume that the leading zero is not required for the time sheet to be correct.
So maybe we can allow for the ID to have a leading zero in the global file, but then—silently or with a message—omit it from the sheet, just to avoid confusion.