Encrypting `brokers.toml`, account and ledger files for `git`

[goodboy]

Since there's often API keys, special private networking config stuff and maybe even account numbers stored in this file we should probably support out of the box git-crypting of some sort to avoid users being paranoid about their git service providers :face_in_clouds:

Also, obviously users may want to encrypt trades ledgers and account files from the .accounting subsys so as to not leak their current positions to the world :joy:

Definitely relates to #530 :sunglasses:

git python APIs

• [ ] https://github.com/jelmer/dulwich#getting-started
• [ ] TODO add more!

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git Encryption repos

Here's an off the cuff list of projects that might be handy for this, mostly pulled from a summary blog post:

• [ ] git-crypt

• https://github.com/AGWA/git-crypt

• https://www.agwa.name/projects/git-crypt/

• [ ] git-easy-crypt

  • https://github.com/taojy123/git-easy-crypt
  • https://taojy123.github.io/git-easy-crypt/

• [ ] git-remote-gcrypt

  • https://github.com/spwhitton/git-remote-gcrypt
  • https://spwhitton.name/tech/code/git-remote-gcrypt/

• [ ] blackbox (from SO oddly enough)

  • https://github.com/StackExchange/blackbox

• [ ] docker secrets

  • https://docs.docker.com/engine/swarm/secrets/

prolly more discussion to come.