Chore: Replace `AWS S3` with `Backblaze B2`

[nelsonic]

As noted in #91 and previously in dwyl/technology-stack#63 AWS S3,
while reasonably straightforward to use, is significantly more expensive than Backblaze B2:
https://www.backblaze.com/b2/cloud-storage-pricing.html

For an image service where we expect the downloads to exceed storage GBs by 10:1
meaning a 1mb image will be viewed 10 times, the most important cost is the downloads.

We already use Cloudflare for our DNS and DDoS protection so we are familiar with the interface.
But we haven't yet used their CDN service ... it appears to be included with no extra monthly bandwidth cost ...
https://www.cloudflare.com/en-gb/plans/

I cannot understand how there is - or at least appears to be - no incremental cost
for bandwidth/downloads through Cloudflare CDN:
https://www.cdnplanet.com/compare/cloudfront/cloudflare/

Obviously none of this matters if nobody is using the upload service ... 🦗🦗🦗
But if we deduce from the popularity of image sharing services/apps that we're building a product people want, 📷 📱 🖼️ ❤️
then keeping a close eye on costs is the only way ensure we don't burn through all our cash 💸
before reaching product-market-fit. ⏳

Todo

• Investigate the Backblaze B2 REST API:
  • https://help.backblaze.com/hc/en-us/articles/360047425453-Getting-Started-with-the-S3-Compatible-API
  • https://www.backblaze.com/docs/cloud-storage-call-the-native-api
  • Create a New Repo to capture the SPIKE (tutorial) of uploading to B2:
    https://github.com/dwyl/backblaze-b2-tutorial if that goes well we can proceed further. 🤞
    • Document everything you learn along the way uploading to B2 including:
      • Sign-up to a "free" [EU-based] account
      • Read the B2 API Docs and figure out how to upload using HTTPoison
    • Possible starting point: https://github.com/yoavlt/B2 (sadly, not maintained, but some useful looking code) 💭
  • If the B2 API is reasonably straightforward we can create a package to abstract everything and use it in imgup.