Merge branch 'ash2k/agent-repo-overview' into 'master'

GitLab Kubernetes Agent repository overview

See merge request gitlab-org/gitlab!49331

doc/.vale/gitlab/spelling-exceptions.txt

@@ -233,6 +233,7 @@ Kubecost
 kubectl
 Kubernetes
 Kubesec
+Kustomize
 Laravel
 ldapsearch
 Lefthook

doc/development/agent/repository_overview.md

+---
+stage: Configure
+group: Configure
+info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#designated-technical-writers
+---
+
+# Kubernetes Agent repository overview **(PREMIUM ONLY)**
+
+This page describes the subfolders of the Kubernetes Agent repository.
+[Development information](index.md) and
+[end-user documentation](../../user/clusters/agent/index.md) are both available.
+
+## `build`
+
+Various files for the build process.
+
+### `build/deployment`
+
+A [`kpt`](https://googlecontainertools.github.io/kpt/) package that bundles some
+[Kustomize](https://kustomize.io/) layers and components. Can be used as-is, or
+to create a custom package to install `agentk`.
+
+## `cmd`
+
+Commands are binaries that this repository produces. They are:
+
+- `kas` is the GitLab Kubernetes Agent Server binary.
+- `agentk` is the GitLab Kubernetes Agent binary.
+
+Each of these directories contain application bootstrap code for:
+
+- Reading configuration.
+- Applying defaults to it.
+- Constructing the dependency graph of objects that constitute the program.
+- Running it.
+
+## `examples`
+
+Git submodules for the example projects.
+
+## `internal`
+
+The main code of both `gitlab-kas` and `agentk`, and various supporting building blocks.
+
+### `internal/agentk`
+
+Main `agentk` logic, including the API implementation for agent modules.
+
+### `internal/api`
+
+Structs that represent some important pieces of data.
+
+### `internal/gitaly`
+
+Items to work with [Gitaly](../../administration/gitaly/index.md).
+
+### `internal/gitlab`
+
+GitLab REST client.
+
+### `internal/kas`
+
+API implementation for the server modules. It contains nothing else, as all server logic
+is split into server modules. The bootstrapping glue that wires the modules together
+is in `cmd/kas/kasapp`.
+
+### `internal/module`
+
+Modules that implement server and agent-side functionality.
+
+### `internal/tool`
+
+Various building blocks. `internal/tool/testing` contains mocks and helpers
+for testing. Mocks are generated with [`gomock`](https://pkg.go.dev/github.com/golang/mock).
+
+## `it`
+
+Contains scaffolding for integration tests. Unused at the moment.
+
+## `pkg`
+
+Contains exported packages.
+
+### `pkg/agentcfg`
+
+Contains protobuf definitions of the `agentk` configuration file. Used to configure
+the agent through a configuration repository.
+
+### `pkg/kascfg`
+
+Contains protobuf definitions of the `gitlab-kas` configuration file. Contains an
+example of that configuration file along with the test for it. The test ensures
+the configuration file example is in sync with the protobuf definitions of the
+file and defaults, which are applied when the file is loaded.