Document setup/config of third-party services (or strip out)

[patcon]

This issue is for figuring out which services we still want to keep, and track progress in documenting (and testing) their setup. If we don't feel they belong anymore, this can track our stripping out the code paths and comments.

• [x] Google for translating comments https://github.com/pol-is/polisServer/pull/319
• [ ] Twitter app for login https://github.com/pol-is/polisServer/issues/254
  • [ ] Facebook app for login https://github.com/pol-is/polisServer/issues/77
• [x] Mailgun for email with file exports https://github.com/pol-is/polis/pull/433
• [x] Amazon Simple Email Service (SES) for text email https://github.com/pol-is/polis/pull/433
• [x] Intercom for support -- [strip out?]
  • https://github.com/compdemocracy/polis/pull/1233
  • alt: https://github.com/compdemocracy/polis/pull/1547
• [ ] Slack API token for chatbot (posting interactive slack messages)
  • https://github.com/compdemocracy/polis/pull/852
  • alt: https://github.com/compdemocracy/polis/pull/1234
• [ ] Slack app for chatbot (slack oauth) -- [strip out? seems unused]
  • https://github.com/compdemocracy/polis/pull/852
  • alt: https://github.com/compdemocracy/polis/pull/1234
• [ ] Stripe for payments -- [strip out?]
  • https://github.com/compdemocracy/polis/pull/1235
  • new: https://github.com/compdemocracy/polis/pull/1620
• [ ] Canvas LMS course support (incl LTI Tools) https://github.com/compdemocracy/polis/pull/1236
• [ ] Postmark for email (commented out) -- [strip out?]
• [ ] Akismet for comment spam filtering
• [ ] Maxmind for city or zipcode from IP (among other insights)
• [ ] Pushover for admin error notifications (commented out) -- [strip out?]
• [ ] Cloudflare for cache purge (commented out)
• [ ] Google for geocoding addresses to latlong

This look ok? Are any of these obviously in need of stripping from codebase?

[patcon]

Did a bit more exploration of what each is used for, and added context. I've got it in rough guess of priority :)

[patcon]

Added docs and minor changes to make Google Translate config work more easily: https://github.com/patcon/polisServer/compare/feature/twitter-login-docs...patcon:feature/doc-google-translate-setup

(Instead of requiring a special command to reformat the credentials key, we just store it as base64.)

Since it built on some docs in FB or Twitter PRs, I branched off that. (Can rebase if the order of merging PRS is untenable.)

EDIT: Confirmed it works fine btw:

[patcon]

Now that typescript conversion is on its way to being done, I've started working on removing some unused features.

After looking over the required changes, the easiest removals (and proper order) seems to be:

1. remove intercom https://github.com/compdemocracy/polis/pull/1233
2. remove slack https://github.com/compdemocracy/polis/pull/1234
3. remove stripe (incl plans/coupons) https://github.com/compdemocracy/polis/pull/1235
4. remove canvas LMS routes/tables https://github.com/compdemocracy/polis/pull/1236

Thoughts?