Better suupport for ORDER and ORDERLABEL in mets:div page elements

[kba]

          > (from https://www.loc.gov/standards/mets/mets.xsd)

So, no, I don't think we should enforce unique @ORDER.

@kba, but IMO we have to respect DFG's application profile for METS here, too. Version 2.3.1 says regarding physical structMap in section 2.2.2.1 (on p.14):

• The ORDER attribute has to contain a numerical sorting value,
  which is used to bring the individual pages into their correct
  physical sequence.
• The ORDERLABEL attribute can contain the pagination of the
  individual page according to the original.
• The LABEL attribute can include the foliation of the individual
  page or the specification of record side and track number.

So regarding the options you presented in #1133,

1. ocrd workspace update-page --order ... --order-label ... --type ... $PAGE_ID which changes/adds the attributes to the mets:div with @ID $PAGE_ID
2. Add these attributes to ocrd workspace add/bulk-add,

I would have preferred option 2 for setting.

See #821 for getting that info on the CLI.

Originally posted by @bertsky in #1134 (comment)