Improve user-preferences test

[ochan12]

Related issue

Closes #868

Context / Background

Adds an extensive suite of tests to user-preferences.js and a couple of fixes
as a consequence of these tests.

What change is being introduced by this PR?

I tried to get 100% coverage on the test going over all the functions.
Some preferences like theme, view, language were not being updated while testing so I
had to change the bitwise assignment clause. Also added the validation for overall-balance-start-date and update-remind-me-after.

How will this be tested?

The issue is about tests :)

---

• I confirm I'm a native or fluent speaker of the language I'm translating to.

[codecov]

Codecov Report

Merging #880 (008611b) into main (b0d2fc8) will increase coverage by 2.24%.
The diff coverage is 100.00%.

❗ Current head 008611b differs from pull request most recent head 241e2c9. Consider uploading reports for the commit 241e2c9 to get more accurate results

@@            Coverage Diff             @@
##             main     #880      +/-   ##
==========================================
+ Coverage   71.99%   74.24%   +2.24%     
==========================================
  Files          17       17              
  Lines        1721     1747      +26     
  Branches      264      268       +4     
==========================================
+ Hits         1239     1297      +58     
+ Misses        482      450      -32     

Impacted Files	Coverage Δ
js/user-preferences.js	100.00% <100.00%> (+26.01%)	⬆️

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[araujoarthur0]

Awesome contribution! Left some comments mostly about consistency, but I love this :)

[araujoarthur0]

\changelog-update
Message: Enhancement [#868]: Improve User Preferences tests