Added support of custom email domain on normalizeEmail

[saharme]

{{ briefly describe what you have done in this PR }}

Checklist

• [X] PR contains only changes related; no stray files, etc.
• [X] README updated (where applicable)
• [X] Tests written (where applicable)

Resolves issue https://github.com/validatorjs/validator.js/issues/1571

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 87.50000% with 1 line in your changes missing coverage. Please review.

Project coverage is 99.94%. Comparing base (d1a9b6d) to head (3d53dfc). Report is 312 commits behind head on master.

Files with missing lines	Patch %	Lines
src/lib/normalizeEmail.js	87.50%	1 Missing :warning:

Additional details and impacted files

@@             Coverage Diff             @@
##            master    #1667      +/-   ##
===========================================
- Coverage   100.00%   99.94%   -0.06%     
===========================================
  Files          101      101              
  Lines         1854     1861       +7     
===========================================
+ Hits          1854     1860       +6     
- Misses           0        1       +1     

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[profnandaa]

@saharme -- thanks for your contrib! Please fix the coverage issue.

[islasjuanp]

Hi @saharme

As far as I understand, is_custom_email_domain option is not compatible with the rest of the normalizers (gmail, yahoo, etc.) For example: if the is_custom_email_domain option is set true, the rest of the normalizers are ignored. In addition, this make it hard to use in the express-validator use case where you create the normalizer before knowing the value.

My suggestion is to add different options for custom domains. For example, adding custom_remove_subaddress, custom_remove_dots, etc. The option allow_custom_domains can be added in order to enable this normalizer.

cc: @profnandaa

[tux-tn]

ping @saharme