fix: added null or empty checks for basic auth credentials

[asadali214]

What

This PR fixes a bug when username/password in CoreHelper.getBase64EncodedCredentials is null or empty, and encoded their combination.

Why

We need to fail the validation if an authentication parameter value is set to an empty string.

Closes #97

Type of change

Select multiple if applicable.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause a breaking change)
• Tests (adds or updates tests)
• Documentation (adds or updates documentation)
• Refactor (style improvements, performance improvements, code refactoring)
• Revert (reverts a commit)
• CI/Build (adds or updates a script, change in external dependencies)

Dependency Change

N/A

Breaking change

N/A

Testing

Unit tests are added to test the new functionality

Checklist

• My code follows the coding conventions
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added new unit tests

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

See analysis details on SonarCloud