Release v0.3.21

In this release:

d8c2601 reqs update
56bc5c6 openssl versions not parsing correctly; additional logger config (#259)
a854980 Configurable settings for downloads (#255)
80ebd62 minor refactor (#254)
1a6aad5 [CveXplore-241] database migrations upgrade added to mainupdate workflow (#250)
284871d minor
87886e8 [CveXplore-246] Centralized configuration throughout the lib; paves the way for #241 (#249)
faa5af3 Format Python code with psf/black (#248)
a1a1e3c added alembic folder to setup.py; addresses #241
0c3b1f1 database models (part of #214) (#247)
a997398 Database migration class added (part of #214) (#244)
129cbba removed stale issue action
22f3dab moved mongodb connection in it's own folder
31f8c21 Added ID's to stub class
bfaa247 First refactor for multiple backend (part of #213) (#233)
d635c19 Format Python code with psf/black (#229)
616bc5d Setup generic logging (#228)
8ebfe15 refactor
4a0991b Format Python code with psf/black (#225)
2f26922 refactor
15434d1 refactor