ci: add go generate check

.github/actions/install_docgen/action.yml

@@ -0,0 +1,26 @@
+name: Install Docgen
+description: |
+  Install Docgen
+runs:
+  using: "composite"
+  steps:
+    - name: Checkout talos
+      uses: actions/checkout@93ea575cb5d8a053eaa0ac8fa3b40d7e05a33cc8 # tag=v3.1.0
+      with:
+        fetch-depth: 0
+        repository: "siderolabs/talos"
+        ref: "v1.2.6"
+        path: talos
+
+    # This is required to be able to build docgen
+    - name: Remove go.work
+      shell: bash
+      working-directory: talos
+      run: rm go.work*
+
+    - name: Install Docgen
+      shell: bash
+      working-directory: talos/hack/docgen
+      run: |
+        go build -o docgen .
+        mv docgen /usr/local/bin

.github/workflows/test-go-generate.yml

@@ -0,0 +1,52 @@
+name: Go generate check
+
+on:
+  workflow_dispatch:
+  push:
+    branches:
+      - main
+      - "release/**"
+  pull_request:
+
+jobs:
+  go-generate:
+    runs-on: ubuntu-22.04
+    steps:
+      - name: Checkout
+        uses: actions/checkout@93ea575cb5d8a053eaa0ac8fa3b40d7e05a33cc8 # tag=v3.1.0
+        with:
+          path: constellation
+          ref: ${{ github.head_ref }}
+
+      - name: Setup Go
+        uses: actions/setup-go@c4a742cab115ed795e34d4513e2cf7d472deb55f # tag=v3.3.1
+        with:
+          go-version: "1.19.3"
+          cache: true
+          cache-dependency-path: constellation/go.mod
+
+      - name: Install docgen
+        uses: ./constellation/.github/actions/install_docgen
+
+      - name: Install stringer
+        shell: bash
+        run: go install golang.org/x/tools/cmd/stringer@latest
+
+      - name: Get Go submodules
+        id: submods
+        shell: bash
+        working-directory: constellation
+        run: |
+          mods=$(go list -f '{{.Dir}}' -m | xargs)
+          echo "Found mods: $mods"
+          echo "submods=${mods}" >> "$GITHUB_OUTPUT"
+
+      - name: Go generate check
+        shell: bash
+        working-directory: constellation
+        run: |
+          mods="${{ steps.submods.outputs.submods }}"
+          for mod in $mods; do
+              go generate $mod/...
+          done
+          git diff --exit-code