[Feature] Add partial masking feature

[kzanetty]

Status

IN REVIEW

Whats?

Add the option for a new blacklist where some properties do not need to be fully masked anymore. New rules can be applied to them for partial masking.

Why?

We need a way to display the card BINs, and the option to apply a custom partial mask would solve this problem.

How?

Add a new parameter, which is a dictionary where the key is the property to be masked and the value is a function that applies a specific masking rule to that property.

Definition of Done:

• [x] Increases API documentation
• [ ] Implements integration tests
• [x] Implements unit tests
• [ ] Is there appropriate logging included?
• [ ] Does this add new dependencies?
• [ ] Does need add new version in changelog?
• [x] Does need update readme, contributing, etc?
• [ ] Does need change in CI server?
• [ ] Will this feature require a new piece of infrastructure be implemented?
• [ ] Does this PR require a blog post? If so, ensure marketing has signed off on content.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 100.00%. Comparing base (20ae088) to head (1f99665).

:exclamation: Current head 1f99665 differs from pull request most recent head 29af657

Please upload reports for the commit 29af657 to get more accurate results.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #8 +/- ## ========================================= Coverage 100.00% 100.00% ========================================= Files 1 1 Lines 33 56 +23 Branches 10 17 +7 ========================================= + Hits 33 56 +23 ```

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