Retry requests to GitLab API

Closes #152

See merge request !496

Misc cleanups

See merge request !495

=== RUN   TestMakeGitLabRequest_HappyPath
    controller.go:137: missing call(s) to *mock_gitlab_access.MockGitlabAccess_MakeRequestClient.Send(equals trailer:{} with 1 option(s)) cmd/agentk/agentkapp/api_test.go:329
    controller.go:137: missing call(s) to *mock_gitlab_access.MockGitlabAccess_MakeRequestClient.CloseSend() cmd/agentk/agentkapp/api_test.go:332
    controller.go:137: aborting test due to missing call(s)

Fix/improve agentk make request method

Closes #151

See merge request !493

Propose default namespace for CI tunnel

See merge request !492

New container image for CI

Closes #148

See merge request !491

Explicitly track mockgen version

See merge request !490

Technical proposal: default values and group level agent authorization

See merge request !427

Update project name in readme

See merge request !488

Document that cache is conditional in Gitaly

See merge request !487

Remove outdated doc

See merge request !485

The up to date one: https://docs.gitlab.com/ee/user/clusters/agent/repository.html

Document implicit configuration

See merge request !484

Filter tunnels based on gRPC service and method

Closes gitlab-org/gitlab#339085

See merge request !483

Post agent configuration

See merge request !434

Fix the expected KAS config for development

See merge request !482

Detect stale generated files in CI

Closes #67

See merge request !478

Bump deps

See merge request !481

Fix marshaling bug in JsonBox

See merge request !480

Embed JsonBox into field

See merge request !479

JsonBox helper for correct JSON marshaling

See merge request !477

Impersonation support in CI tunnel

See merge request !471