Investigate if we could de-hardcode /usr/src/app

[anthonyfok]

[wishlist, low priority; applies to OpenDRR/model-factory too]

Right now, a lot of the code has the path /usr/src/app, which is the WORKDIR of the python-opendrr Docker Compose service (?). Would be nice if it could be de-hardcoded, so, for example, add_data.sh and friends may be run outside of Docker, if there is ever a desire to do so.

Might be tricky though, especially in the PostgresSQL scripts. There is the :variable syntax that we could use in the SQL scripts, but how flexible is that in reality, that remains to be seen.

So, is this feasible or worth pursuing at all? Don't know.
Assigning myself to this issue right now so I don't forget, but will likely ask Drew and Will to help if and when we are much less busy. :-)