proofs api refactor

[LesnyRumcajs]

Summary of changes

Changes introduced in this pull request:

• refactored the proofs API module a bit, which includes:
  • separating the files, logically
  • adjusting visibility
  • adding docs (and adjusting current ones to reflect reality) - addressing @aatifsyed remark
  • adding tests where the logic was more than trivial
  • code-golfing

Reference issue to close (if applicable)

Closes

Other information and links

Change checklist

• I have performed a self-review of my own code,
• I have made corresponding changes to the documentation,
• I have added tests that prove my fix is effective or that my feature works (if possible),
• I have made sure the CHANGELOG is up-to-date. All user-facing changes should be reflected in this document.

[hanabi1224]

Maybe worth mentioning in doc somewhere
https://lotus.filecoin.io/kb/nodes-in-china/

Running Lotus requires the download of chain’s proof parameters which are large files which by default are hosted outside of China and very slow to download there. To get around that, users should set the following environment variable when running either of lotus, lotus-miner and lotus-worker:

export IPFS_GATEWAY=https://proof-parameters.s3.cn-south-1.jdcloud-oss.com/ipfs/

[hanabi1224]

At first glance I feel we should prefix the environment variable with FOREST_ but in this case maybe it's more convenient to re-use the lotus one. They don't prefix it with LOTUS_ for some reason.

[LesnyRumcajs]

I was a bit hesitant to change the variable names to avoid breaking changes, but better do it now than later.

[ruseinov]

At first glance I feel we should prefix the environment variable with FOREST_ but in this case maybe it's more convenient to re-use the lotus one. They don't prefix it with LOTUS_ for some reason.

Agreed on the prefix. As stated above - it would be nice to have some sort of tool that would allow us to specify the prefix for everything we load. Then we can load variables with and without the prefix.

[LesnyRumcajs]

@hanabi1224 Great point there, I was not aware of that. On top of that, I was able to find a bug (not sure how long it was there, I guess pretty long) where the IPFS_GATEWAY was not overridable - the environment variable only changed what was logged. 🤡 See a4c53c5