Database Improvement Fixes

[JayDwee]

Summary

close #106

Checklist

• [x] This PR fixes an issue.
• [ ] 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 #424 (c3939d6) into master (d671c6f) will increase coverage by 0.55%. The diff coverage is 92.00%.

@@            Coverage Diff             @@
##           master     #424      +/-   ##
==========================================
+ Coverage   87.49%   88.05%   +0.55%     
==========================================
  Files         130      130              
  Lines        9214     9207       -7     
==========================================
+ Hits         8062     8107      +45     
+ Misses       1152     1100      -52     

Flag	Coverage Δ
unittests	88.05% <92.00%> (+0.55%)	:arrow_up:

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

Files	Coverage Δ
koala/cogs/base/models.py	89.28% <100.00%> (ø)
koala/cogs/intro_cog/models.py	88.88% <100.00%> (ø)
koala/cogs/react_for_role/core.py	73.39% <100.00%> (+5.21%)	:arrow_up:
koala/cogs/react_for_role/models.py	90.32% <100.00%> (ø)
koala/cogs/text_filter/models.py	89.28% <100.00%> (ø)
koala/cogs/twitch_alert/models.py	92.30% <100.00%> (ø)
koala/cogs/verification/core.py	81.92% <ø> (ø)
koala/cogs/voting/models.py	89.47% <100.00%> (ø)
koala/db.py	94.73% <100.00%> (-0.17%)	:arrow_down:
tests/cogs/react_for_role/test_cog.py	90.32% <100.00%> (+4.58%)	:arrow_up:
... and 1 more

... and 1 file with indirect coverage changes