DB initializing only checks whether environment variable is set, but not whether it is 1 or 0

[Zethson]

Describe the bug

When messing around with the setup I set the FLASK_DEBUG env to 0.
However, MegaQC expects it to be unset.

Expected behavior

I expect MegaQC to treat those special ENVs as unset if equal to 0.

[multimeric]

It's true that this is a little unintuitive. It's not a particularly simple fix because even FLASK_DEBUG=0 is actually setting the variable to the string "0" which is a truthy value in Python. A more stable solution might be to use something like this library: https://pypi.org/project/env-flag/.