feat: Add an artifact auto-assignment example

The example comes with a minimal test pipeline. It will be extended to
the other modules in another contribution.

.github/workflows/CI.yml

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+name: Tests
+
+permissions: read-all
+
+on:
+  push:
+    branches:
+  pull_request:
+
+jobs:
+  tests:
+    strategy:
+      matrix:
+        tuleap_functions:
+          - "artifact-post-action/auto-assign"
+    build:
+        runs-on: ubuntu-22.04
+        name: Tests (${{ matrix.tuleap_functions }})
+        steps:
+          - uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # v4.1.1
+          - uses: cachix/install-nix-action@6004951b182f8860210c8d6f0d808ec5b1a33d28 # v25
+          - run: cd "${{ matrix.tuleap_functions }}"
+          - name: Prepare
+            run: nix-shell --pure --run "make prepare"
+          - name: Tests
+            run: nix-shell --pure --run "make tests"
+          - name: Build
+            run: nix-shell --pure --run "make build"

artifact-post-action/auto-assign/.gitignore

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+dist/
+node_modules/

artifact-post-action/auto-assign/Makefile

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+.PHONY: prepare
+prepare:
+	pnpm install --frozen-lockfile
+
+.PHONY: tests
+tests:
+	pnpm run typecheck
+	pnpm run test
+
+.PHONY: build
+build:
+	pnpm run build

artifact-post-action/auto-assign/README.md

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+# Artifact post action: automatically assign a contributor
+
+This Function automatically assigns the creator of an artifact as the contributor/assignee.
+The contributor/assignee is only set when the artifact is created if no other contributors
+have been designed.
+
+The code expects the tracker to have the [contributor/assignee semantic](https://docs.tuleap.org/user-guide/trackers/administration/configuration/semantics.html#contributor-assignee) set.
+
+## How to test
+
+First you need to run `nix-shell` to have all needed tools.
+
+Then build the Tuleap Function with:
+```shell
+make prepare
+make build
+```
+
+You can then run it with:
+
+```shell
+wasmtime run ./dist/function.wasm < sample.json
+```
+
+You can run unit tests with:
+
+```shell
+make tests
+```
+
+## How to use
+
+Create a tracker and define the [contributor/assignee semantic](https://docs.tuleap.org/user-guide/trackers/administration/configuration/semantics.html#contributor-assignee).
+
+Then build the function:
+
+```shell
+make prepare
+make build
+```
+
+Then upload the binary result file (`dist/function.wasm`) to your Tracker
+administration (Administration > Workflow > Tuleap Functions).
+
+And finally, create an artifact, shortly after the creation, the contributor field will automatically be set to yourself.

artifact-post-action/auto-assign/javy.nix

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+# TODO:
+# * build from sources
+# * upstream to nixpkgs
+{ stdenv
+, lib
+, fetchurl
+, autoPatchelfHook
+, gzip
+}:
+
+stdenv.mkDerivation rec {
+  pname = "javy";
+  version = "1.4.0";
+
+  src = fetchurl {
+    url = "https://github.com/bytecodealliance/javy/releases/download/v${version}/javy-x86_64-linux-v${version}.gz";
+    hash = "sha256-NZIzT8BdtgKiE3RbePWEY1E5TWe9mr2LSRhhmxzWzd8=";
+  };
+
+  nativeBuildInputs = [
+    autoPatchelfHook
+    gzip
+  ];
+
+  buildInputs = [
+    stdenv.cc.cc.lib
+  ];
+
+  unpackPhase = ''
+    runHook preUnpack
+    gzip -cd "${src}" > javy
+    runHook postUnpack
+  '';
+
+  installPhase = ''
+    runHook preInstall
+    install -m755 -D javy $out/bin/javy
+    runHook postInstall
+  '';
+
+  meta = with lib; {
+    homepage = "https://github.com/bytecodealliance/javy";
+    description = "JS to WebAssembly toolchain";
+    license = licenses.asl20;
+  };
+}

artifact-post-action/auto-assign/package.json

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+{
+  "name": "@tuleap/functions-post-action-auto-assign",
+  "version": "0.0.0",
+  "private": true,
+  "scripts": {
+    "build": "pnpm run build:bundle && pnpm run build:js2wasm && pnpm run build:wasmopt",
+    "build:bundle": "esbuild src/main.ts --platform=node --bundle --target=es2022 --minify --outfile=dist/function.js",
+    "build:js2wasm": "javy compile ./dist/function.js -o ./dist/function-unoptimized.wasm",
+    "build:wasmopt": "wasm-opt -O2 ./dist/function-unoptimized.wasm -o ./dist/function.wasm",
+    "typecheck": "tsc --noEmit",
+    "test": "vitest run"
+  },
+  "keywords": [],
+  "author": "Enalean Team",
+  "license": "MIT",
+  "devDependencies": {
+    "esbuild": "^0.20.0",
+    "typescript": "^5.3.3",
+    "vitest": "^1.2.2"
+  },
+  "dependencies": {
+    "javy": "^0.1.2"
+  }
+}