IMPR: `src` layout

[d-v-b]

Improvement Request

Move source code under the src prefix. I.e., instead of the source code being stored in datajoint , the source code would be stored in src/datajoint.

This is consistent with current best practices for python packaging because it ensures that tests do not accidentally pull in resources other than the built version of the software being tested.

[github-actions]

This issue is stale because it has been open for 45 days with no activity.

[github-actions]

This issue is stale because it has been open for 45 days with no activity.