feat(bot): add HTTP route

[tschaffter]

• Fixes Add a custom HTTP route to the bot #754
• Fixes Identify how to best scaffold the bot app #846

Changelog

• Add dedicated app class.
• Add custom API endpoints using an Express server and serverless-http.
  • Add path /challenge-bot/ping (/ping is reserved by AWS API Gateway).
• Simulate serverless deployment with serverless-offline.

Features

Deploy the bot locally in a serverless environment:

vscode@cdaa8ec69ba2:/workspaces/challenge-registry/apps/challenge-bot$ sls offline
Compiling with Typescript...
Using local tsconfig.json - tsconfig.json
Warning: "rootDir" from local tsconfig.json is overriden
Typescript compiled.
Watching typescript files...

Starting Offline at stage dev (us-east-1)

Offline [http for lambda] listening on http://localhost:3002
Function names exposed for local invocation by aws-sdk:
           * challengeBot: challenge-bot-dev-challengeBot
           * ping: challenge-bot-dev-ping

   ┌────────────────────────────────────────────────────────────────────────────────┐
   │                                                                                │
   │   POST | http://localhost:3000/api/github/webhooks                             │
   │   POST | http://localhost:3000/2015-03-31/functions/challengeBot/invocations   │
   │   GET  | http://localhost:3000/challenge-bot/ping                              │
   │   POST | http://localhost:3000/2015-03-31/functions/ping/invocations           │
   │                                                                                │
   └────────────────────────────────────────────────────────────────────────────────┘

Server ready: http://localhost:3000 🚀

Ping the local app:

$ curl -i -X GET http://localhost:3000/challenge-bot/ping
HTTP/1.1 200 OK
content-type: application/json; charset=utf-8
content-length: 13
etag: W/"d-NMovXDE1NuzTr1lpmBE8ZRjliFM"
cache-control: no-cache
accept-ranges: bytes
Date: Sun, 23 Oct 2022 00:31:25 GMT
Connection: keep-alive
Keep-Alive: timeout=5

{"pong":true}

Ping the app deployed to AWS:

$ curl -i -X GET https://3p2dbilegi.execute-api.us-east-1.amazonaws.com/challenge-bot/ping
HTTP/2 200 
date: Sun, 23 Oct 2022 00:30:47 GMT
content-type: application/json; charset=utf-8
content-length: 13
etag: W/"d-NMovXDE1NuzTr1lpmBE8ZRjliFM"
apigw-requestid: abqwThDlIAMESdA=

{"pong":true}