Update README with instructions

Author: Mirch

README.md

@@ -1 +1,60 @@
 # rust-lambda-starter
+
+This is a template for starting serverless projects with AWS Lambda, Rust, and Tofu.
+
+## Components
+
+The project contains:
+- a Cargo project with an empty library and a **hello_world** binary representing an example Lambda function;
+- a Python script for building all the Lambda funtions present in the `./src/bins` directory;
+- a base infrastructure written in OpenTofu with IAM, Lambda, and API Gateway resources;
+- a CI pipeline that triggers on any PR against the `main` branch or any commit to the `main` branch;
+- a CD pipeline that triggers on any push to the `main` branch.
+
+## Usage
+
+### Getting the project
+
+To get a local copy of the template, either use [pont](https://github.com/soupdevsolutions/pont):
+
+```bash
+pont build --name <your-project-name> --from https://github.com/soupdevsolutions/rust-lambda-starter
+```
+
+or clone the repository and change the occurences of the template name:
+
+```bash
+git clone https://github.com/soupdevsolutions/rust-lambda-starter ./<your-project-name>
+cd <your-project-name>
+
+# rename the occurences using bash or your IDE tooling
+TEMPLATE_NAME_KEBAB_CASE=rust-lambda-starter
+TEMPLATE_NAME_SNAKE_CASE=rust_lambda_starter
+PROJECT_NAME=<your-project-name>
+
+find . \( -name \*.rs -o -name \*.tf -o -name \*.toml -o -name \*.md -o -name \*.lock \) -exec sed -i '' "s#$TEMPLATE_NAME_KEBAB_CASE#$PROJECT_NAME#g" {} \;
+find . \( -name \*.rs -o -name \*.tf -o -name \*.toml -o -name \*.md -o -name \*.lock \) -exec sed -i '' "s#$TEMPLATE_NAME_SNAKE_CASE#$PROJECT_NAME#g" {} \;
+```
+
+### Deployment
+
+The recommended way for deploying the project is to use GitHub Actions; however, you can also do it from your local machine.  
+
+For deploying with GitHub Actions, push your project to a new repository, go to the repository's **Settings** -> **Secrets and variables** -> **Actions**, and add secrets for your IAM user credentials:
+- AWS_ACCESS_KEY_ID -> the access key id
+- AWS_SECRET_ACCESS_KEY -> the secret access key
+Any push to the `main` branch will trigger both the CI and CD pipelines.
+
+If you choose to deploy from your local machine, make sure to follow the guide for [configuring the AWS CLI](https://docs.aws.amazon.com/cli/v1/userguide/cli-chap-configure.html), so OpenTofu can deploy to your AWS account. Then, you can run all the steps from the CD pipeline locally:
+
+```bash
+# init OpenTofu (only needs to be done once locally)
+tofu -chdir=infrastructure init
+
+# build the Lambda functions
+python3 ./scripts/build.py
+
+# plan and apply the changes
+tofu -chdir=infrastructure plan
+tofu -chdir=infrastructure apply
+```