Feature/verify api

[JayDwee]

Summary

close #397

Checklist

• [x] This PR fixes an issue.
• [x] This PR adds something new (e.g. new method or parameters).
• [ ] This PR is a breaking change (e.g. methods or parameters removed/renamed)
• [ ] This PR is not a code change (e.g. documentation, README, ...)

• [x] Have you tested the changes? (pytest & dpytest)
• [x] Have you followed PEP-8 for naming and styling?
• [x] Has your code been properly documented with RestructuredText docstrings?
• [x] Have you added your changes to CHANGELOG.md under the [Unreleased] heading?
• [ ] If your code added new bot commands, have you updated documentation.json?

• [x] All of this code is your own, or follows the author repo's licence.

[codecov[bot]]

Codecov Report

Merging #405 (0f8d07b) into master (44492c8) will decrease coverage by 0.04%. The diff coverage is 90.47%.

@@            Coverage Diff             @@
##           master     #405      +/-   ##
==========================================
- Coverage   87.39%   87.35%   -0.04%     
==========================================
  Files         119      123       +4     
  Lines        8750     8916     +166     
==========================================
+ Hits         7647     7789     +142     
- Misses       1103     1127      +24     

Flag	Coverage Δ
unittests	87.35% <90.47%> (-0.04%)	:arrow_down:

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
koala/cogs/announce/db.py	100.00% <ø> (ø)
koala/cogs/colour_role/cog.py	88.10% <ø> (ø)
koala/cogs/colour_role/models.py	88.88% <ø> (ø)
koala/cogs/react_for_role/api.py	91.66% <ø> (ø)
koala/cogs/react_for_role/utils.py	100.00% <ø> (ø)
koala/cogs/twitch_alert/env.py	100.00% <ø> (ø)
koala/cogs/twitch_alert/models.py	92.68% <ø> (ø)
koala/cogs/verification/env.py	100.00% <ø> (ø)
koala/env.py	81.25% <ø> (ø)
tests/cogs/base/test_cog.py	100.00% <ø> (ø)
... and 60 more

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[abluey]

All the code looks good, though is db file really needed in verification? I moved the blacklist stuff there but every other db action was executed in core anyway 🤔