fix: Merge welcome and email verification mail

[iamareebjamal]

Fixes fossasia/open-event-frontend#5410

[codecov]

Codecov Report

Merging #7399 into development will increase coverage by 0.01%.
The diff coverage is 28.57%.

@@               Coverage Diff               @@
##           development    #7399      +/-   ##
===============================================
+ Coverage        64.57%   64.59%   +0.01%     
===============================================
  Files              262      262              
  Lines            13249    13246       -3     
===============================================
  Hits              8556     8556              
+ Misses            4693     4690       -3     

Impacted Files	Coverage Δ
app/api/helpers/system_mails.py	100.00% <ø> (ø)
app/api/users.py	31.28% <28.57%> (+0.51%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update a1ea1d0...db5f151. Read the comment docs.