Migrate relevant documentation to `data-sources-app` repository

[maxachis]

Fixes

• 13

Description

• Move api_docs folder to data-sources-app
• Move data-dictionaries to data sources app
• Except for record-types-taxonomy, which has been moved into terminology.md

Testing

• Evaluate that documentation moved from this directory is as expected and conforming to #13

Performance

• Documentation, so minimal performance impact.

Docs

• lol