Resolve "HELLO WORLD: as a dev i want to send users a message from the cli"

Notes

Closes #17 (closed)

With this PR...

A dev can use the provided bash scripts to:

• install signal-cli
• configure it as a systemd process that can send and receive messages on the system dbus
• authorize it to control a user-provided signal phone number

They should provide an .env file with the following variables defined:

SIGNAL_CLI_VERSION
SIGNAL_CLI_PATH
SIGNAL_CLI_PASSWORD
RELAY_NUMBER
VERIFICATION_CODE

They can then start up the app with:

$ systemctl start signal-cli
$ yarn dev

Running the following will cause the message "hello world!" to be sent to 555-555-5555 and 444-444-4444 over Signal from whatever phone number the dev has registered as $RELAY_NUMBER:

$ curl -i -H 'Content-type: application/json'  \
  -d '{ "message": "hello world!", "recipients": ["+15555555555", "+14444444444"] }' \
  localhost:3000/relay

Up next: registering some phone numbers with twilio so we can test this ish in CI!!!!