Add end-to-end tests for specific endpoints

[blkt]

Here's a list of endpoints not covered by smoke tests, ordered by least-covered-first (in terms of unit tests). Note that coverage of routines used by these handlers might be different from the one reported here, and that number is only used for prioritization.

• UpdateProject -> /api/v1/projects (31.40%)
• GetProvider -> /api/v1/providers/{name} (47.80%)
• PatchProvider -> /api/v1/providers (47.80%)
• ListProviders -> /api/v1/providers (47.80%)
• DeleteRepositoryByName2 -> /api/v1/repository/name/{name} (62.70%)
• RegisterRepository2 -> /api/v1/repository/register (62.70%)
• CreateUser -> /api/v1/user (63.30%)