docs: add build and packaging overview

Signed-off-by: Miguel Martinez <miguel@chainloop.dev>
Entire-Checkpoint: c53099c636f6

Author: migmartri

docs/build-and-packaging.md

@@ -0,0 +1,113 @@
+# Chainloop Build and Packaging Overview
+
+## Release Flow
+
+The release process starts by pushing a **git tag** matching `v*.*.*`, which triggers the `release.yaml` GitHub Actions workflow.
+
+```
+Tag push (v1.x.x) → Tests → GoReleaser build → Signing → Helm chart bump PR
+```
+
+## Building with GoReleaser
+
+All binaries and container images are built via [GoReleaser](https://goreleaser.com/) (`.goreleaser.yml` at the repo root).
+
+### Binaries
+
+| Binary | Platforms | Notes |
+|--------|-----------|-------|
+| `control-plane` | linux/amd64, linux/arm64 | Main backend service |
+| `artifact-cas` | linux/amd64, linux/arm64 | Content-addressable storage proxy |
+| `chainloop` (CLI) | darwin/amd64, darwin/arm64, linux/amd64, linux/arm64 | Multi-platform client |
+| `chainloop-plugin-discord-webhook` | linux/amd64 | Bundled into control-plane image |
+| `chainloop-plugin-smtp` | linux/amd64 | Bundled into control-plane image |
+| `chainloop-plugin-dependency-track` | linux/amd64 | Bundled into control-plane image |
+
+All binaries are statically compiled (`CGO_ENABLED=0`) and stripped (`-s -w`). Version info is injected via `-ldflags` from the git tag. CLI binaries are published as GitHub Release assets alongside a `checksums.txt`.
+
+### Container Images
+
+GoReleaser uses **Docker buildx with QEMU** to produce multi-architecture images (amd64 + arm64), published to **GitHub Container Registry** (`ghcr.io/chainloop-dev/chainloop/`).
+
+| Image | Base | Dockerfile |
+|-------|------|------------|
+| `control-plane` | `scratch` | `app/controlplane/Dockerfile.goreleaser` |
+| `control-plane-migrations` | `arigaio/atlas` | `app/controlplane/Dockerfile.migrations` |
+| `artifact-cas` | `scratch` | `app/artifact-cas/Dockerfile.goreleaser` |
+| `cli` | `scratch` | `app/cli/Dockerfile.goreleaser` |
+
+**Tagging strategy:**
+- Platform-specific: `<image>:<tag>-amd64`, `<image>:<tag>-arm64`
+- Unified manifest: `<image>:<tag>` and `<image>:latest`
+
+### Signing
+
+All container images and release artifacts are signed with **Cosign** using a private key.
+
+## Building Dependency Container Images
+
+We don't consume upstream Bitnami container images directly. Instead, we **rebuild them from source** using the Dockerfiles in the [bitnami/containers](https://github.com/bitnami/containers) repository. This gives us full control over the build process, allows us to sign images with our own key, and host them in our own registry.
+
+This is handled by the **`build_external_container_images.yaml`** workflow, triggered manually via `workflow_dispatch`.
+
+### How it works
+
+1. The workflow checks out the `bitnami/containers` repo at a **pinned commit SHA** for reproducibility.
+2. Builds each image for **linux/amd64 + linux/arm64** using Docker buildx.
+3. Pushes to GHCR under `ghcr.io/chainloop-dev/chainloop/`.
+4. Signs the resulting image with Cosign.
+
+### Images built
+
+| Image | Version | Bitnami Source Path |
+|-------|---------|---------------------|
+| `postgresql` | 16.4.0 | `bitnami/postgresql/16/debian-12` |
+| `postgres-exporter` | 0.15.0 | `bitnami/postgres-exporter/0/debian-12` |
+| `os-shell` | 12 | `bitnami/os-shell/12/debian-12` |
+| `dex` | 2.43.1 | `bitnami/dex/2/debian-12` |
+| `vault` | 1.17.3 | `bitnami/vault/1/debian-12` |
+| `vault-csi-provider` | 1.4.3 | `bitnami/vault-csi-provider/1/debian-12` |
+| `vault-k8s` | 1.4.2 | `bitnami/vault-k8s/1/debian-12` |
+| `nginx-ingress-controller` | 1.12.1 | `bitnami/nginx-ingress-controller/1/debian-12` |
+| `nginx` | 1.27.4 | `bitnami/nginx/1.27/debian-12` |
+
+Each image is tagged with its app version, `latest`, and the git SHA.
+
+## Helm Chart
+
+### Location
+
+The main Helm chart lives at **`deployment/chainloop/`**.
+
+### Dependencies
+
+Sub-charts are **vendored** (committed under `deployment/chainloop/charts/`) as `file://` dependencies:
+
+| Sub-chart | Source | Condition |
+|-----------|--------|-----------|
+| `common` | Bitnami Common | Always (template utilities) |
+| `postgresql` | Bitnami PostgreSQL | `postgresql.enabled` |
+| `vault` | Bitnami Vault | `development` flag |
+| `dex` | Custom | `development` flag |
+
+All sub-chart container image references point to our own GHCR rebuilds (e.g., `ghcr.io/chainloop-dev/chainloop/postgresql:16.4.0`), not upstream Bitnami or Docker Hub.
+
+### Chart Bumping on Release
+
+After a successful release, the workflow creates a **PR** that:
+
+1. Bumps `appVersion` to the new tag (e.g., `v1.79.1`).
+2. Increments the chart version.
+3. Updates image tag references in `values.yaml`.
+
+This is handled by `.github/workflows/utils/bump-chart-and-dagger-version.sh`.
+
+## Local Development Builds
+
+```bash
+# Build binaries only (snapshot, current platform)
+make build_devel
+
+# Build binaries + container images locally (no signing)
+make build_devel_container_images
+```