feat: Enable the user to add their custom masking
feat: Enable the user to add their custom masking

- The user can either specify their custom masking symbol or a whole
word to be placed instead of the data being replaced
Request sample:
```
{
    "Locale": "en_US",
    "Text": "This should be masked as it is a credit card 4111111111111111(VISA). This too should be masked as it is a North American phone number 1-(555)-555-5555? The service can also mask Social Security Numbers like this one: 555-55-5555",
    "MaskSymbol": "(hidden)"
}
```

Signed-off-by: Adrian Oprea <a1b909ec1cc11cce40c28d3640eab600e582f833@codesi.nz>

opreaadrian/message-masking-service