Remove last non-Avram keys from exported schema

[pkiraly]

@nichtich I am fine with removing unitLenght, but I would like to keep the repeatableContent flag at least when it is true. We can remove it when it is false (because that is the normal case). Could you imagine to put repeatableContent to Avram schema?

[nichtich]

I hesitate to add more cases and rules to core Avram, especially when there are alternatives. Adding repeatableContent would require to clearly define its semantics. How about an alternative to codes for repeatable elements:

{
  "positions":{
    "01-04":{
      "label":"Illustrations",
      "url":"https://www.loc.gov/marc/bibliographic/bd006.html",
      "flags": {  ← like codes but repeatable to fill length of 4 characters
        " ":{"label":"No illustrations"}, ← length of flag (here 1 for " ") must be proper divisor of 4
        "a":{"label":"Illustrations"},
        "b":{"label":"Maps"},

[pkiraly]

I am fine with this solution, so you can go further with it in this PR. I have however some concerns that potential future users of Avram will find it a bit confusing that same thing have different names.

[nichtich]

Avram specification 0.9.6 contains flags as part of data element definitions in positions with an example from MARC 21 Bibliographic field 008. There is a corresponding validation rule invalidFlag.

I'm extending the pull request to also solve #402.

[pkiraly]

I adjusted the UNIMARC schema reader to adapt the current changes (flags and codelist).

[pkiraly]

@nichtich What is the status of this PR? You wrote „I'm extending the pull request to also solve #402” but there were no more commits after this comment.

[nichtich]

Thanks for reminder. I directly committed to the main branch with an update.