Add MySQL FAQ section

[zeripath]

MySQL is the ultimate root cause of repeated issues on here. We have the gitea convert command for some of the most common problems, however we should add a section to the FAQ to cover some of the most glaring repeated problems:

Signed-off-by: Andrew Thornton [email protected]

[codecov-commenter]

Codecov Report

Merging #12780 into master will decrease coverage by 0.03%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #12780      +/-   ##
==========================================
- Coverage   43.26%   43.23%   -0.04%     
==========================================
  Files         649      649              
  Lines       72046    72046              
==========================================
- Hits        31169    31146      -23     
- Misses      35838    35855      +17     
- Partials     5039     5045       +6     

Impacted Files	Coverage Δ
modules/util/timer.go	42.85% <0.00%> (-42.86%)	⬇️
modules/notification/mail/mail.go	34.48% <0.00%> (-3.45%)	⬇️
modules/notification/ui/ui.go	80.55% <0.00%> (-2.78%)	⬇️
models/unit.go	46.57% <0.00%> (-2.74%)	⬇️
modules/process/manager.go	72.50% <0.00%> (-2.50%)	⬇️
services/pull/check.go	47.69% <0.00%> (-2.31%)	⬇️
modules/git/blame.go	75.43% <0.00%> (-1.76%)	⬇️
modules/queue/unique_queue_disk_channel.go	53.84% <0.00%> (-1.54%)	⬇️
models/notification.go	66.13% <0.00%> (-0.92%)	⬇️
models/error.go	34.81% <0.00%> (-0.86%)	⬇️
... and 4 more

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