Use Mailhog for E-mail testing

Info from DOC: I have added this for both Digital Access and IdM

@Jonas: Correct to structure it like this?

Mailhog is a tool that can be used when testing sending emails with Smart ID components Digital Access and Identity Manager.

Useful commands

Start mailhog

<SMARTIDHOME>/tools/mailhog/docker-compose up -d

Stop mailhog

<SMARTIDHOME>/tools/mailhog/docker-compose stop

Mailhog logs

<SMARTIDHOME>/tools/mailhog/docker-compose logs -f

Edit <SMARTIDHOME>/tools/mailhog/docker-compose.yml and change the ports to the left of the colons. Restart the container to apply the changes
Change ports
```
    ports:
      - 1025:1025 # smtp server
      - 8025:8025 # web ui
```
Configure your Smart ID component with the following settings if mailhog is deployed to the same host as the component. If mailhog is deployed to another host, replace the SMTP host with the hostname/ip address, and make sure that the Smart ID host can access mailhog on port 1025.
```
SMTP Host: mailhog
SMTP Port: 1025
Sender: test@example.com
```
Access the web interface to see emails. Browse to the host where mailhog is deployed on port 8025.
Access emails
```
http://SMARTID-HOST>:8025
```