Add unit tests for Contact class

[Banji0x]

Description This PR adds comprehensive unit tests for the Contact class in com.fleencorp.feen.model.domain.share. The tests cover nullability, non-nullability, equality, and non-equality scenarios, following our code guidelines and test patterns.

Changes Implement ContactTest class using JUnit 5 Follow patterns from FleenFeenEntityTest and Oauth2AuthorizationTest Use snake_case for @Test method names Add tests for Contact object creation and property validation

Test Coverage

1. New tests cover:
2. Nullability and non-nullability checks for all properties
3. Equality and non-equality comparisons

[aalamu]

@Banji0x We can add a bullet point for the list of things we implemented in our PR like

• Created a unit test for Contact class.
• Followed patterns of unit test as found in FleenFeenEntityTest and Oauth2AuthorizationTest
• Use snake_case for @Test case method names.
• Add test cases for Contact object creation and property validation

Note:

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