Data type mappings need a single source of truth

[jh-RLI]

Description of the issue

We need to use type mappings to birdge the different type terms. In JSON-Schema and PostgreSQL types are named diffrently.

Currently OMI and also other tools like oem2orm and also the OEP API (the PostgreSQL types) provide thier own type mappings.

Ideas of solution

Harmonize the multiple mapping sources into one.

• We need to find a place to define the mappings.
• Collect and clearify all mappings

Workflow checklist

• I am aware of the workflow in CONTRIBUTING.md