feat: add base64 encode transformation

[tty2]

Thank you for contributing to Coraza WAF, your effort is greatly appreciated
Before submitting check if what you want to add to coraza list meets quality standards before sending pull request. Thanks!

This PR brings base64Encode method.
Issue 1252

This changes rely on encoding/base std library base64.StdEncoding.EncodeToString
I spent a little bit of time to investigate if it's necessary to implement custom base64Encode. If you have any doubts, real cases where std doesn't work or not appropriate for this project, please let me know here.

Make sure that you've checked the boxes below before you submit PR:

• My code includes positive and negative tests.
  As long as this implementation is technically a one liner that relies on std lib there is no real reason make unit test for it, otherwise we'll test std lib.
  Plus as I can see there is a ready test data for base64encode in transformation/testdata/base64encode.json which is used in TestTransformations.
  Plus I see there is no test.go files for the other one liners (ex. hexEncode), as I understood just to avoid bloating the codebase.
• I have an appropriate description with correct grammar.
  This code follows the code style in the project: has a specific signature with 3 returning parameters (string, bool, error) as I understand for the future flexibility and compatibility.
• I have read Contribution guidelines, maintainers note and Quality standard.
• My code is properly linted and passes pre-commit tests.
  I ran CGO_ENABLED=1 go run mage.go check on my local machine and didn't get any fail.

Thanks for your contribution ❤️

[fzipi]

Can you please add tests?

Take a look at the original tests and try to replicate those :)

[tty2]

@fzipi

Can you please add tests?

Take a look at the original tests and try to replicate those :)

Could you clarify please what should be done?
I currently run tests and these cases run as well.
Quick prove with println in a screenshot

Do you mean add test cases to this json?

[fzipi]

Ah, good catch! They are already there! Don't need to add them 😄

[fzipi]

LGTM! Thanks for your contribution!

[fzipi]

I wonder why tests didn't run :/

[fzipi]

Ok, I forced a small update to the date to force running local tests :)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.69%. Comparing base (dcdbc28) to head (fdaf31f).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1257   +/-   ##
=======================================
  Coverage   81.68%   81.69%           
=======================================
  Files         168      169    +1     
  Lines        9762     9767    +5     
=======================================
+ Hits         7974     7979    +5     
  Misses       1537     1537           
  Partials      251      251           

Flag	Coverage Δ
coraza.rule.case_sensitive_args_keys	81.65% <100.00%> (+<0.01%)	⬆️
coraza.rule.multiphase_valuation	81.69% <100.00%> (+<0.01%)	⬆️
coraza.rule.no_regex_multiline	81.63% <100.00%> (+<0.01%)	⬆️
default	81.69% <100.00%> (+<0.01%)	⬆️
examples+	16.55% <20.00%> (+<0.01%)	⬆️
examples+coraza.rule.case_sensitive_args_keys	81.65% <100.00%> (+<0.01%)	⬆️
examples+coraza.rule.multiphase_valuation	81.52% <100.00%> (+<0.01%)	⬆️
examples+coraza.rule.no_regex_multiline	81.55% <100.00%> (+<0.01%)	⬆️
examples+memoize_builders	81.65% <100.00%> (+<0.01%)	⬆️
examples+no_fs_access	80.97% <100.00%> (+<0.01%)	⬆️
ftw	81.69% <100.00%> (+<0.01%)	⬆️
memoize_builders	81.78% <100.00%> (+<0.01%)	⬆️
no_fs_access	81.14% <100.00%> (+<0.01%)	⬆️
tinygo	81.66% <100.00%> (+<0.01%)	⬆️

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