OMI rewrite

[christian-rli]

OMI has several issues. Most importantly it's difficult to maintain and needlessly convoluted. It should reliably perform a handful of tasks and be less of everything else. @henhuy now has time time to address this in a radical rewrite. This issue is a meta level discussion space and collects things to be done.

@wingechr : you are warmly invited to ask for features, make structural remarks and get involved if you like. The goal is to have a tool that you and all of us enjoy using.

Broad plan:

• base OMI's functions on the schema.json alone
• Get rid of all the version and key specific classes and declutter the whole project
• Write new functions and tests for validation and conversion

Things OMI should reliably do after the rewrite:

• validate metadata json
• validate that tables match metadata description
• conversion of metadata from old to new (supported versions 1.5.2, 1.6 and 2.0)
• return useful error messages
• API can call OMI to validate uploads. Error messages (both from API itself and from OMI) should find their way back to the user.

Related info:

• The oemetadata builder will also get an update.
• OMI should be a helpful feature for the csv upload wizard. When dropping a csv file into the upload area, if it's reasonably structured, the OEP should be able to infer the structure and datatype from the first few lines and create a table. Limitations may apply.

[jh-RLI]

I will merge the PR ... i think the requirements in this issue are already implemented. More updates follow in new PR´s.