Cover list of controllers and handlers with tests

### Description
1. Write integration tests for the following endpoints in the listed controllers.
2. Write unit tests for the corresponding handlers.
3. Identify and fix any issues flagged by SonarQube rules within the provided directories.

SourcesController:
1. GET /api/Sources/GetAllNames - GetAllNames
2. GET /api/Sources/GetAllCategories - GetAllCategories
3. GET /api/Sources/GetCategoryById/{id:int} - GetCategoryById
4. GET /api/Sources/GetCategoryContentByStreetcodeId/{categoryId:int}&{streetcodeId:int} - GetCategoryContentByStreetcodeId
5. GET /api/Sources/GetCategoriesByStreetcodeId/{streetcodeId:int} - GetCategoriesByStreetcodeId
6. POST /api/Sources/CreateCategory - CreateCategory
7. PUT /api/Sources/UpdateCategory - UpdateCategory
8. DELETE /api/Sources/DeleteCategory/{id:int} - DeleteCategory

PaymentController:
1. POST /api/Payment/CreateInvoice - CreateInvoice

PartnersController:
1. GET /api/Partners/GetAllShort - GetAllShort
2. GET /api/Partners/GetPartnersByIsKeyPartner/{isKeyPartner:bool} - GetPartnersByIsKeyPartner
3. PUT /api/Partners/Update - Update
4. DELETE /api/Partners/Delete/{id:int} - Delete

NewsController:
1. GET /api/News/GetById/{id:int} - GetById
2. GET /api/News/GetByUrl/{url} - GetByUrl
3. GET /api/News/GetNewsAndLinksByUrl/{url} - GetNewsAndLinksByUrl
4. POST /api/News/Create - Create
5. DELETE /api/News/Delete/{id:int} - Delete
6. PUT /api/News/Update - Update

Locate the SourcesController, PaymentController, PartnersController, and NewsController implementations and their corresponding handlers, then inspect existing integration and unit test patterns. Cover the listed endpoints with integration tests and the corresponding handlers with unit tests. Run the relevant test suites and SonarQube checks; done means the requested endpoints and handlers are tested and reported SonarQube issues in the provided directories are addressed.

Written by the indexing model from the issue text.