Deploy `calendar-backend` to EC2

Currently, the calendar-backend is deployed to EC2.

This guide will describe how to deploy on a new EC2 machine and how to configure the deployment pipeline.

First we need to launch a new EC2 instance
1. Choose Amazon Linux as OS and a 64 bit architecture
2. Instance type: t2.nano This is the cheapest and smallest instance type.
3. Choose calendar-backend as the key pair Or we can create a new key pair, just make sure to update the github secret (details will follow in a step below).
4. Use calendar-backend security group Or we can create a new security group, we will need the following ports to be added under the inbound rules:
  - 22 - SSH port used by our github-actions workflow to deploy new version of calendar-backend
  - 80 - used by certbot to renew the TLS certificate (details will follow in a step below)
  - 8080 - this is the port that calendar-backend uses
5. Allocate a 30 GB gp3 disk
6. Create S3 bucket for DB backup
  - Set calendar-db-backup as the name and use eu-central-1 as the region:
  - Keep ACLs disabled as object ownership option:
  - Block public access:
  - Enable versioning:
  - Use default encryption:
7. Create a new IAM Policy for S3 put access:
  - Choose S3 as the service and PutObject as access level:
  - Add a new ARN for calendar-db-backup bucket and database.db3 file:
  - Use calendar_db_backup as the pollicy name:
8. Create a new IAM role
  - Choose AWS service as the trusted entity type:
  - Use EC2 as the use case:
  - Choose the previously created IAM Policy under permissions policies:
  - Use calendar_db_backup as the name:
9. Attach role to EC2 instance:
  - Choose the EC2 instance, then click on Actions, then click on Modify IAM role under Security
  - Choose the previously created IAM role:
10. Configure cron on EC2
  - SSH into the EC2 machine
  - Install crond because it's not present by default:
    - install cronie
```
sudo dnf install cronie
```
    - enable crond
```
sudo systemctl enable crond
```
    - check that crond is running as expected
```
sudo systemctl status crond
```
      The result should look like:
```
● crond.service - Command Scheduler
Loaded: loaded (/usr/lib/systemd/system/crond.service; enabled; preset: enabled)
Active: active (running) since Tue 2024-04-16 06:59:54 UTC; 4min 57s ago
Main PID: 1858743 (crond)
Tasks: 2 (limit: 510)
...
```
  - install sqlite
```
sudo yum install sqlite-devel
```
  - create a new file db_backup.sh in home directory (/home/ec2-user):
```
cd /home/ec2-user
sqlite3 database.db3 ".backup 'database_backup.db3'"
aws s3 cp database.db3 s3://calendar-db-backup/database.db3
rm database_backup.db3
```
  - give exec permissions to the previous file:
```
chmod +x db_backup.sh
```
  - run:
```
echo "0 0,6,12,18 * * * root /home/ec2-user/db_backup.sh" | sudo tee -a /etc/crontab > /dev/null
```
    This will upload the database to S3 bucket every day at 00:00, 06:00, 12:00, 18:00 UTC time
Configure the TLS certificate by following the tutorial from here.

Note that you will have to ssh into the EC2 machine for setting the certificate. To do this we will need:
- the private key from the key pair that we chose on instance creation from above
- the public DNS of our EC2 instance. This can be found in AWS console on instance details
- run the following command from a terminal:
```
ssh -i PATH_TO_SSH_KEY ec2-user@EC2_PUBLIC_DNS
```
Also make sure that the calendar-backend is pointing to the correct certificate.
Configure the deployment pipeline. For this we will have to update a few github secrets:
- SSH_PRIVATE_KEY - this should be the private key of the key pair configured on EC2 from above
- REMOTE_HOST - this should be the public DNS of our EC2 instance
- REMOTE_USER - set this to ec2-user
- CALENDAR_JWT_SIGNING_KEY - the secret key used by the calendar-backend to sign jwt tokens
Finally we can trigger Deploy to EC2 workflow to deploy calendar-backend to the newly created EC2 instance

You can find a sequence diagram explaining the process of deploying to EC2 here.

Deploy calendar-backend to EC2

Deploy `calendar-backend` to EC2