New tests

[davfsa]

• Rename some properties for consistency
• Rename format_* args for consitency

Summary

Checklist

• I have run nox and all the pipelines have passed.
• I have made unittests according to the code I have added/modified/deleted.

Related issues

#47

[codecov-commenter]

Codecov Report

Merging #50 into master will increase coverage by 0.45%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #50      +/-   ##
==========================================
+ Coverage   79.37%   79.83%   +0.45%     
==========================================
  Files          77       77              
  Lines        9630     9630              
  Branches     1233     1233              
==========================================
+ Hits         7644     7688      +44     
+ Misses       1931     1887      -44     
  Partials       55       55              

Impacted Files	Coverage Δ
hikari/applications.py	100.00% <100.00%> (ø)
hikari/channels.py	100.00% <100.00%> (ø)
hikari/guilds.py	96.14% <100.00%> (+12.12%)	⬆️
hikari/invites.py	86.41% <100.00%> (ø)
hikari/users.py	100.00% <100.00%> (ø)
hikari/webhooks.py	67.16% <100.00%> (ø)

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[ghost]

I think we should name format to something else to prevent builtin shadowing.

Maybe ext for file extension?