Display relevant weeks on exam timetable

[not-a-scam]

Context

Initially just created to close #1717

Additionally updated exam timetable to only display the week when exams to be taken are happening. Previously, the first week will always be displayed even if there are no exams to be taken.

Implementation

Full Week Display

• Check if there is a Saturday exam and display full week if there is
• Change cell width to be equal across days with the addition of Sunday

Display relevant weeks

1. Filter out examinable mods from visible mods
2. Map visible and examinable mods to their exam dates
3. Reduce by comparison to get first and last exam dates
4. Normalise result to always be a Monday
5. Calculate number of weeks for display

Other Information

First PR here! Feedback is appreciated!

• Created it so that if there are no exams, the getExamCalendar would return the current date as the first date instead for simplicity, but not sure if there are better return value? Considered using the first day of exams from the academic calendar but I thought the additional call would be unnecessary since the value isn't used.

• I think the addition of Sunday looks fine on mobile. Seemed to be a concern in Exams on Saturday should show full week #1717 but included a gif for reference

[greptile-apps]

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[vercel]

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 56.44%. Comparing base (988c6fd) to head (24cf382).
⚠️ Report is 244 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4418      +/-   ##
==========================================
+ Coverage   54.52%   56.44%   +1.91%     
==========================================
  Files         274      317      +43     
  Lines        6076     6963     +887     
  Branches     1455     1683     +228     
==========================================
+ Hits         3313     3930     +617     
- Misses       2763     3033     +270     

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