Git: Add test for http bearer token auth

Add a test case for http bearer token in

source-controller/controllers/gitrepository_controller_test.go

Lines 334 to 336 in 9dc4271

// TODO: Add test case for HTTPS with bearer token auth secret. It
// depends on gitkit to have support for bearer token based
// authentication.

once bearer token authentication support is added in gitkit, refer fluxcd/gitkit#11, and gittestserver.

Refer fluxcd/pkg#442 for more discussions around bearer token support.