Stricter domain name pattern in email regex

[mrsdizzie]

Fixes #6735

[codecov-io]

Codecov Report

Merging #6739 into master will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #6739      +/-   ##
==========================================
- Coverage      41%   40.98%   -0.02%     
==========================================
  Files         421      421              
  Lines       57915    57915              
==========================================
- Hits        23746    23735      -11     
- Misses      31010    31021      +11     
  Partials     3159     3159

Impacted Files	Coverage Δ
modules/markup/html.go	81% <ø> (ø)	⬆️
models/unit.go	45.71% <0%> (-5.72%)	⬇️
models/repo_indexer.go	66.52% <0%> (-1.28%)	⬇️
models/repo_list.go	66.84% <0%> (-1.06%)	⬇️
routers/repo/view.go	41.6% <0%> (-1.01%)	⬇️

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[lunny]

Please send backport to release/v1.8

[mrsdizzie]

This can't be cherry picked because of 6293736 which also changes this line. Want me to create a separate commit on release/v1.8 that just does the same thing?

[techknowlogick]

@mrsdizzie yes please