Unit tests for skill Tree Backend

[raj1802]

Issue Description

To ensure the reliability and correctness of the Skill Tree Backend APIs by developing comprehensive unit tests that cover various scenarios and edge cases, thereby preventing defects and improving the overall quality of the application.

Following are the unit tests to be implemented

• unit tests for skills API, getAll() method #162
• Unit tests for create() method in skillServiceImplementation class for Skills API #163
• Unit tests for approveRejectSkillRequest() method in skillServiceImplementation class for Skills API #164
• Unit tests for getRequestsByStatus() method
• Unit tests for approveRejectSkillRequest() method
• Unit tests for getAllEndorsementsBySkillId() method in EndorsementServiceImplementation class for Skills API #165
• Unit tests for create endorsement method in in EndorsementServiceImplementation class for Skills API #168
• Unit tests for update endorsement method