chore: add devcontainer contributor workflow

Author: t-col

.devcontainer/Dockerfile

@@ -0,0 +1,6 @@
+ARG JAVA_VERSION=8
+FROM eclipse-temurin:${JAVA_VERSION}-jdk-jammy
+
+RUN apt-get update \
+    && apt-get install -y --no-install-recommends curl git openssh-client \
+    && rm -rf /var/lib/apt/lists/*

.devcontainer/devcontainer.json

@@ -0,0 +1,20 @@
+{
+  "name": "contentful.java",
+  "build": {
+    "dockerfile": "Dockerfile",
+    "context": "..",
+    "args": {
+      "JAVA_VERSION": "${localEnv:JAVA_VERSION:8}"
+    }
+  },
+  "workspaceFolder": "/workspaces/${localWorkspaceFolderBasename}",
+  "remoteUser": "vscode",
+  "postCreateCommand": "./mvnw -B -q -DskipTests dependency:go-offline",
+  "customizations": {
+    "vscode": {
+      "extensions": [
+        "redhat.java"
+      ]
+    }
+  }
+}

.github/workflows/ci.yml

@@ -0,0 +1,25 @@
+name: CI
+
+on:
+  push:
+    branches: [master]
+  pull_request:
+    branches: [master]
+
+permissions:
+  contents: read
+
+jobs:
+  test:
+    name: Test (Java 8)
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Run tests in dev container
+        uses: devcontainers/ci@v0.3
+        env:
+          JAVA_VERSION: "8"
+        with:
+          push: never
+          runCmd: ./mvnw -B test

.travis.yml

@@ -0,0 +1,21 @@
+# Contributing
+
+Thanks for helping improve `contentful.java`.
+
+## Development with Dev Containers
+
+This repository includes a `.devcontainer` configuration for a reproducible local setup. GitHub Actions uses the same devcontainer configuration for CI.
+
+1. Install Docker and a devcontainer-compatible editor. Visual Studio Code with the Dev Containers extension works well.
+2. Open the repository in the dev container and wait for the post-create setup to finish.
+3. Verify the environment:
+
+```bash
+./mvnw -B test
+```
+
+## Pull Requests
+
+1. Fork the repository and create a branch for your change.
+2. Run the relevant checks from the dev container.
+3. Open a pull request with a short summary of the change and any follow-up context.

CONTRIBUTING.md

@@ -12,7 +12,7 @@
 
 contentful.java - Contentful Java Delivery Library
 ==================================================
-[![Build Status](https://travis-ci.org/contentful/contentful.java.svg)](https://travis-ci.org/contentful/contentful.java/builds#)
+[![CI](https://github.com/contentful/contentful.java/actions/workflows/ci.yml/badge.svg)](https://github.com/contentful/contentful.java/actions/workflows/ci.yml)
 
 > Java library for [Content Delivery API](https://www.contentful.com/developers/docs/references/content-delivery-api/) and [Content Preview API](https://www.contentful.com/developers/docs/references/content-preview-api/). It helps in easily accessing the content stored in Contentful using Java applications.
 
@@ -513,6 +513,16 @@ Getting involved
 
 [![PRs Welcome](https://img.shields.io/badge/PRs-welcome-brightgreen.svg?maxAge=31557600)](http://makeapullrequest.com)
 
+For a reproducible local setup, open this repository in its included dev container. The container installs the project dependencies automatically when it is created.
+
+After the container is ready, run:
+
+```bash
+./mvnw -B test
+```
+
+See [CONTRIBUTING.md](CONTRIBUTING.md) for the full contributor workflow.
+
 Code of Conduct
 ===============