feat: add GET /api/v1/organisations/{organisationId} endpoint

[C3Techie]

Resolves #679

Description

• What was changed: Added a new endpoint GET /api/v1/organisations/{organisationId} to retrieve an organisation by its ID.
• Why it was changed: The feature was implemented to allow users to retrieve organisation details by its unique ID.

Changes Implemented

• Implemented the getOrganisationById method in the OrganisationService class to retrieve an organisation by its ID.
• Added a new GET /api/v1/organisations/{organisationId} endpoint in the OrganisationController class.
• Created integration tests for the GET endpoint in the e2e test class to validate functionality for both valid and invalid organisation IDs.
• Added unit tests in the OrganisationServiceTest class for the getOrganisationById method to ensure correct behavior for existing and non-existing organisation IDs.
• Updated the response handling in the service to throw a NotFoundException when the organisation is not found.

Manual testing performed: Validated API with Postman to ensure correct response for both valid and invalid organisation IDs:

• Screenshot from Postman
  Valid Organization ID Response

Invalid Organization ID Response

Screenshot from Swagger

POST request to create an Organisation

GET Organisation by ID