Avram schema validation

[nwagner84]

Specification: https://format.gbv.de/schema/avram/specification

• Add Avram schema parser
• Add --schema parameter

[nichtich]

See this issue for a list of error types. I did not find JUnit XML a good fit to express error results.

[nwagner84]

My current plan is to extend the current validation (valid PICA+ record or not) by the validation against an Avram schema. This means to add a new parameter to almost all commands to take an Avram schema into account and skip invalid records (if the parameter is set) or stop the processing (if the flag is not set).

The second step is the lint command (see #117) with an Avram linter (among other linters). At this point the error output format is important (and JUnit was a first idea). I'll definitely look at the linked issue when choosing a good output format.

[nwagner84]

In the meantime, a small team at the DNB created the experimental pica-linter tool, which focus on pica filter expression for validaten (besides other lints). This works very well and the tool will enter the beta-phase until the end of year.

I close this ticket, because Avram schema validation is no longer necessary.