Type hints are not compatible with Python < 3.9

Summary

See https://gitlab.indiscale.com/caosdb/src/caosdb-webui/-/jobs/104210, where the code is tested with Python 3.7

Expected Behavior

At least Python 3.8 should be supported.

Actual Behavior

Tests fail with Python < 3.9

Steps to Reproduce the Problem

1. Run import caosdb.apiutils with Python < 3.9

Specifications

• Version: Whatever runs on the caosdb-webui pipeline
• Platform: See pipeline settings

Possible fixes

See https://stackoverflow.com/questions/59101121/type-hint-for-a-dict-gives-typeerror-type-object-is-not-subscriptable