Add support for prefix and suffix preservation in FixedLengthMasker

[ehayik]

Why

To add support for preserving prefix and suffix sections during masking.

var masker = Masker.fixedLength(4)
    .preserveSuffix(3)  // Keep last 3 characters unmasked
    .preservePrefix(2)  // Keep first 2 characters unmasked
    .build();

var ssn = "123-45-6789";
var maskedSsn = masker.apply(ssn);
// Result: "12******789"

How

• Added prefixLength and suffixLength fields for preserving sections of the string during masking.
• Updated constructor and builder pattern to allow configuration of the new fields.
• Added a new private method applyWithSuffixAndPrefixPreservation to handle the logic for prefix and suffix preservation during masking.
• Added parameterized tests with various prefix and suffix preservation scenarios.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
94.9% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud